diff --git a/polygerrit-ui/app/elements/checks/gr-checks-tab.ts b/polygerrit-ui/app/elements/checks/gr-checks-tab.ts
index e5386f4..9376a03 100644
--- a/polygerrit-ui/app/elements/checks/gr-checks-tab.ts
+++ b/polygerrit-ui/app/elements/checks/gr-checks-tab.ts
@@ -28,18 +28,23 @@
   allActions$,
   allResults$,
   allRuns$,
+  checksPatchsetNumber$,
   someProvidersAreLoading$,
 } from '../../services/checks/checks-model';
 import './gr-checks-runs';
 import './gr-checks-results';
 import {sharedStyles} from '../../styles/shared-styles';
-import {changeNum$, currentPatchNum$} from '../../services/change/change-model';
-import {NumericChangeId, PatchSetNum} from '../../types/common';
+import {changeNum$, latestPatchNum$} from '../../services/change/change-model';
+import {NumericChangeId, PatchSetNumber} from '../../types/common';
 import {
   ActionTriggeredEvent,
   fireActionTriggered,
 } from '../../services/checks/checks-util';
-import {checkRequiredProperty} from '../../utils/common-util';
+import {
+  assertIsDefined,
+  check,
+  checkRequiredProperty,
+} from '../../utils/common-util';
 import {RunSelectedEvent} from './gr-checks-runs';
 import {ChecksTabState} from '../../types/events';
 import {fireAlert} from '../../utils/event-util';
@@ -64,7 +69,10 @@
   tabState?: ChecksTabState;
 
   @property()
-  currentPatchNum: PatchSetNum | undefined = undefined;
+  checksPatchsetNumber: PatchSetNumber | undefined = undefined;
+
+  @property()
+  latestPatchsetNumber: PatchSetNumber | undefined = undefined;
 
   @property()
   changeNum: NumericChangeId | undefined = undefined;
@@ -82,7 +90,8 @@
     this.subscribe('runs', allRuns$);
     this.subscribe('actions', allActions$);
     this.subscribe('results', allResults$);
-    this.subscribe('currentPatchNum', currentPatchNum$);
+    this.subscribe('checksPatchsetNumber', checksPatchsetNumber$);
+    this.subscribe('latestPatchsetNumber', latestPatchNum$);
     this.subscribe('changeNum', changeNum$);
     this.subscribe('someProvidersAreLoading', someProvidersAreLoading$);
 
@@ -124,7 +133,6 @@
   }
 
   render() {
-    const ps = `Patchset ${this.currentPatchNum} (Latest)`;
     const filteredRuns = this.runs.filter(
       r =>
         this.selectedRuns.length === 0 ||
@@ -134,13 +142,9 @@
       <div class="header">
         <div class="left">
           <gr-dropdown-list
-            value="${ps}"
-            .items="${[
-              {
-                value: `${ps}`,
-                text: `${ps}`,
-              },
-            ]}"
+            value="${this.checksPatchsetNumber}"
+            .items="${this.createPatchsetDropdownItems()}"
+            @value-change="${this.onPatchsetSelected}"
           ></gr-dropdown-list>
           <span ?hidden="${!this.someProvidersAreLoading}">Loading...</span>
         </div>
@@ -163,6 +167,24 @@
     `;
   }
 
+  private onPatchsetSelected(e: CustomEvent<{value: string}>) {
+    const patchset = Number(e.detail.value);
+    check(!isNaN(patchset), 'selected patchset must be a number');
+    this.checksService.setPatchset(patchset as PatchSetNumber);
+  }
+
+  private createPatchsetDropdownItems() {
+    return Array.from(Array(this.latestPatchsetNumber), (_, i) => {
+      assertIsDefined(this.latestPatchsetNumber, 'latestPatchsetNumber');
+      const index = this.latestPatchsetNumber - i;
+      const postfix = index === this.latestPatchsetNumber ? ' (latest)' : '';
+      return {
+        value: `${index}`,
+        text: `Patchset ${index}${postfix}`,
+      };
+    });
+  }
+
   protected updated(changedProperties: PropertyValues) {
     super.updated(changedProperties);
     if (changedProperties.has('tabState')) {
@@ -181,10 +203,10 @@
 
   handleActionTriggered(action: Action, run?: CheckRun) {
     if (!this.changeNum) return;
-    if (!this.currentPatchNum) return;
+    if (!this.checksPatchsetNumber) return;
     const promise = action.callback(
       this.changeNum,
-      this.currentPatchNum as number,
+      this.checksPatchsetNumber,
       run?.attempt,
       run?.externalId,
       run?.checkName,
diff --git a/polygerrit-ui/app/services/change/change-model.ts b/polygerrit-ui/app/services/change/change-model.ts
index b2bdcfe..e7472de 100644
--- a/polygerrit-ui/app/services/change/change-model.ts
+++ b/polygerrit-ui/app/services/change/change-model.ts
@@ -46,10 +46,18 @@
 // Must only be used by the change service or whatever is in control of this
 // model.
 export function updateState(change?: ParsedChangeInfo) {
-  privateState$.next({
-    ...privateState$.getValue(),
-    change,
-  });
+  const current = privateState$.getValue();
+  // We want to make it easy for subscribers to react to change changes, so we
+  // are explicitly emitting and additional `undefined` when the change number
+  // changes. So if you are subscribed to the latestPatchsetNumber for example,
+  // then you can rely on emissions even if the old and the new change have the
+  // same latestPatchsetNumber.
+  if (change !== undefined && current.change !== undefined) {
+    if (change._number !== current.change._number) {
+      privateState$.next({...current, change: undefined});
+    }
+  }
+  privateState$.next({...current, change});
 }
 
 /**
@@ -91,9 +99,6 @@
  *
  * Note that this selector can emit a patchNum without the change being
  * available!
- *
- * TODO: It would be good to assert/enforce somehow that currentPatchNum$ cannot
- * emit 'PARENT'.
  */
 export const currentPatchNum$: Observable<
   PatchSetNum | undefined
diff --git a/polygerrit-ui/app/services/change/change-service.ts b/polygerrit-ui/app/services/change/change-service.ts
index 4524813..c292fb5 100644
--- a/polygerrit-ui/app/services/change/change-service.ts
+++ b/polygerrit-ui/app/services/change/change-service.ts
@@ -16,21 +16,16 @@
  */
 import {routerChangeNum$} from '../router/router-model';
 import {updateState} from './change-model';
-import {tap} from 'rxjs/operators';
 import {ParsedChangeInfo} from '../../types/types';
 
 export class ChangeService {
-  // TODO: In the future we will want to make restApiService.getChangeDetail()
-  // calls from a switchMap() here. For now just make sure to invalidate the
-  // change when no changeNum is set.
-  private routerChangeNumEffect = routerChangeNum$.pipe(
-    tap(changeNum => {
-      if (!changeNum) updateState(undefined);
-    })
-  );
-
   constructor() {
-    this.routerChangeNumEffect.subscribe();
+    // TODO: In the future we will want to make restApiService.getChangeDetail()
+    // calls from a switchMap() here. For now just make sure to invalidate the
+    // change when no changeNum is set.
+    routerChangeNum$.subscribe(changeNum => {
+      if (!changeNum) updateState(undefined);
+    });
   }
 
   /**
diff --git a/polygerrit-ui/app/services/checks/checks-model.ts b/polygerrit-ui/app/services/checks/checks-model.ts
index d8dc688..1c5b862 100644
--- a/polygerrit-ui/app/services/checks/checks-model.ts
+++ b/polygerrit-ui/app/services/checks/checks-model.ts
@@ -26,6 +26,7 @@
   RunStatus,
 } from '../../api/checks';
 import {distinctUntilChanged, map} from 'rxjs/operators';
+import {PatchSetNumber} from '../../types/common';
 
 // This is a convenience type for working with results, because when working
 // with a bunch of results you will typically also want to know about the run
@@ -41,29 +42,44 @@
 }
 
 interface ChecksState {
-  [name: string]: ChecksProviderState;
+  patchsetNumber?: PatchSetNumber;
+  providerNameToState: {
+    [name: string]: ChecksProviderState;
+  };
 }
 
-const initialState: ChecksState = {};
+const initialState: ChecksState = {
+  providerNameToState: {},
+};
 
 const privateState$ = new BehaviorSubject(initialState);
 
 // Re-exporting as Observable so that you can only subscribe, but not emit.
 export const checksState$: Observable<ChecksState> = privateState$;
 
-export const aPluginHasRegistered$ = checksState$.pipe(
+export const checksPatchsetNumber$ = checksState$.pipe(
+  map(state => state.patchsetNumber),
+  distinctUntilChanged()
+);
+
+export const checksProviderState$ = checksState$.pipe(
+  map(state => state.providerNameToState),
+  distinctUntilChanged()
+);
+
+export const aPluginHasRegistered$ = checksProviderState$.pipe(
   map(state => Object.keys(state).length > 0),
   distinctUntilChanged()
 );
 
-export const someProvidersAreLoading$ = checksState$.pipe(
+export const someProvidersAreLoading$ = checksProviderState$.pipe(
   map(state => {
     return Object.values(state).some(providerState => providerState.loading);
   }),
   distinctUntilChanged()
 );
 
-export const allActions$ = checksState$.pipe(
+export const allActions$ = checksProviderState$.pipe(
   map(state => {
     return Object.values(state).reduce(
       (allActions: Action[], providerState: ChecksProviderState) => [
@@ -75,7 +91,7 @@
   })
 );
 
-export const allRuns$ = checksState$.pipe(
+export const allRuns$ = checksProviderState$.pipe(
   map(state => {
     return Object.values(state).reduce(
       (allRuns: CheckRun[], providerState: ChecksProviderState) => [
@@ -87,7 +103,7 @@
   })
 );
 
-export const checkToPluginMap$ = checksState$.pipe(
+export const checkToPluginMap$ = checksProviderState$.pipe(
   map(state => {
     const map = new Map<string, string>();
     for (const [pluginName, providerState] of Object.entries(state)) {
@@ -99,7 +115,7 @@
   })
 );
 
-export const allResults$ = checksState$.pipe(
+export const allResults$ = checksProviderState$.pipe(
   map(state => {
     return Object.values(state)
       .reduce(
@@ -124,7 +140,8 @@
   config?: ChecksApiConfig
 ) {
   const nextState = {...privateState$.getValue()};
-  nextState[pluginName] = {
+  nextState.providerNameToState = {...nextState.providerNameToState};
+  nextState.providerNameToState[pluginName] = {
     pluginName,
     loading: false,
     config,
@@ -200,8 +217,9 @@
 
 export function updateStateSetLoading(pluginName: string) {
   const nextState = {...privateState$.getValue()};
-  nextState[pluginName] = {
-    ...nextState[pluginName],
+  nextState.providerNameToState = {...nextState.providerNameToState};
+  nextState.providerNameToState[pluginName] = {
+    ...nextState.providerNameToState[pluginName],
     loading: true,
   };
   privateState$.next(nextState);
@@ -213,11 +231,18 @@
   actions: Action[] = []
 ) {
   const nextState = {...privateState$.getValue()};
-  nextState[pluginName] = {
-    ...nextState[pluginName],
+  nextState.providerNameToState = {...nextState.providerNameToState};
+  nextState.providerNameToState[pluginName] = {
+    ...nextState.providerNameToState[pluginName],
     loading: false,
     runs: [...runs],
     actions: [...actions],
   };
   privateState$.next(nextState);
 }
+
+export function updateStateSetPatchset(patchsetNumber?: PatchSetNumber) {
+  const nextState = {...privateState$.getValue()};
+  nextState.patchsetNumber = patchsetNumber;
+  privateState$.next(nextState);
+}
diff --git a/polygerrit-ui/app/services/checks/checks-service.ts b/polygerrit-ui/app/services/checks/checks-service.ts
index d2a4775..3ce714a 100644
--- a/polygerrit-ui/app/services/checks/checks-service.ts
+++ b/polygerrit-ui/app/services/checks/checks-service.ts
@@ -18,7 +18,6 @@
 import {
   switchMap,
   takeWhile,
-  tap,
   throttleTime,
   withLatestFrom,
 } from 'rxjs/operators';
@@ -29,12 +28,14 @@
   FetchResponse,
   ResponseCode,
 } from '../../api/checks';
-import {change$, currentPatchNum$} from '../change/change-model';
+import {change$, changeNum$, latestPatchNum$} from '../change/change-model';
 import {
   updateStateSetLoading,
   checkToPluginMap$,
   updateStateSetProvider,
   updateStateSetResults,
+  checksPatchsetNumber$,
+  updateStateSetPatchset,
 } from './checks-model';
 import {
   BehaviorSubject,
@@ -44,18 +45,26 @@
   of,
   Subject,
 } from 'rxjs';
+import {PatchSetNumber} from '../../types/common';
 
 export class ChecksService {
   private readonly providers: {[name: string]: ChecksProvider} = {};
 
   private readonly reloadSubjects: {[name: string]: Subject<void>} = {};
 
-  private changeAndPatchNum$ = change$.pipe(withLatestFrom(currentPatchNum$));
-
   private checkToPluginMap = new Map<string, string>();
 
   constructor() {
-    checkToPluginMap$.subscribe(x => (this.checkToPluginMap = x));
+    checkToPluginMap$.subscribe(map => {
+      this.checkToPluginMap = map;
+    });
+    latestPatchNum$.subscribe(num => {
+      updateStateSetPatchset(num);
+    });
+  }
+
+  setPatchset(num: PatchSetNumber) {
+    updateStateSetPatchset(num);
   }
 
   reload(pluginName: string) {
@@ -82,37 +91,43 @@
     updateStateSetProvider(pluginName, config);
     // Both, changed numbers and and announceUpdate request should trigger.
     combineLatest([
-      this.changeAndPatchNum$,
+      changeNum$,
+      checksPatchsetNumber$,
       this.reloadSubjects[pluginName].pipe(throttleTime(1000)),
     ])
       .pipe(
         takeWhile(_ => !!this.providers[pluginName]),
+        withLatestFrom(change$),
         switchMap(
-          ([[change, patchNum], _]): Observable<FetchResponse> => {
-            if (!change || !patchNum || typeof patchNum !== 'number') {
+          ([[changeNum, patchNum, _], change]): Observable<FetchResponse> => {
+            if (
+              !change ||
+              !changeNum ||
+              !patchNum ||
+              typeof patchNum !== 'number'
+            ) {
               return of({
                 responseCode: ResponseCode.OK,
                 runs: [],
               });
             }
             const data: ChangeData = {
-              changeNumber: change._number,
+              changeNumber: changeNum,
               patchsetNumber: patchNum,
               repo: change.project,
             };
             updateStateSetLoading(pluginName);
             return from(this.providers[pluginName].fetch(data));
           }
-        ),
-        tap(response => {
-          updateStateSetResults(
-            pluginName,
-            response.runs ?? [],
-            response.actions
-          );
-        })
+        )
       )
-      .subscribe(() => {});
+      .subscribe(response => {
+        updateStateSetResults(
+          pluginName,
+          response.runs ?? [],
+          response.actions
+        );
+      });
     this.reload(pluginName);
   }
 }
diff --git a/polygerrit-ui/app/types/common.ts b/polygerrit-ui/app/types/common.ts
index 711b11b..1bfabf8 100644
--- a/polygerrit-ui/app/types/common.ts
+++ b/polygerrit-ui/app/types/common.ts
@@ -76,6 +76,7 @@
 export type ParsedJSON = BrandType<unknown, '_parsedJSON'>;
 
 export type PatchSetNum = BrandType<'PARENT' | 'edit' | number, '_patchSet'>;
+export type PatchSetNumber = BrandType<number, '_patchSet'>;
 
 export const EditPatchSetNum = 'edit' as PatchSetNum;
 // TODO(TS): This is not correct, it is better to have a separate ApiPatchSetNum
diff --git a/polygerrit-ui/app/utils/patch-set-util.ts b/polygerrit-ui/app/utils/patch-set-util.ts
index 40e3eef..af56798 100644
--- a/polygerrit-ui/app/utils/patch-set-util.ts
+++ b/polygerrit-ui/app/utils/patch-set-util.ts
@@ -3,11 +3,12 @@
   ChangeInfo,
   PatchSetNum,
   EditPatchSetNum,
-  BrandType,
   ParentPatchSetNum,
+  PatchSetNumber,
 } from '../types/common';
 import {RestApiService} from '../services/gr-rest-api/gr-rest-api';
 import {EditRevisionInfo, ParsedChangeInfo} from '../types/types';
+import {check} from './common-util';
 
 /**
  * @license
@@ -82,9 +83,7 @@
   return patchset as PatchSetNum;
 }
 
-export function isNumber(
-  psn: PatchSetNum
-): psn is BrandType<number, '_patchSet'> {
+export function isNumber(psn: PatchSetNum): psn is PatchSetNumber {
   return typeof psn === 'number';
 }
 
@@ -250,14 +249,16 @@
 
 export function computeLatestPatchNum(
   allPatchSets?: PatchSet[]
-): PatchSetNum | undefined {
+): PatchSetNumber | undefined {
   if (!allPatchSets || !allPatchSets.length) {
     return undefined;
   }
-  if (allPatchSets[0].num === EditPatchSetNum) {
-    return allPatchSets[1].num;
+  let latest = allPatchSets[0].num;
+  if (latest === EditPatchSetNum) {
+    latest = allPatchSets[1].num;
   }
-  return allPatchSets[0].num;
+  check(isNumber(latest), 'Latest patchset cannot be EDIT or PARENT.');
+  return latest;
 }
 
 export function computePredecessor(