Index: src/applications/people/query/PhabricatorPeopleQuery.php
===================================================================
--- src/applications/people/query/PhabricatorPeopleQuery.php
+++ src/applications/people/query/PhabricatorPeopleQuery.php
@@ -249,10 +249,11 @@
         $this->dateCreatedBefore);
     }
 
-    if ($this->isAdmin) {
+    if ($this->isAdmin !== null) {
       $where[] = qsprintf(
         $conn_r,
-        'user.isAdmin = 1');
+        'user.isAdmin = %d',
+        (int)$this->isAdmin);
     }
 
     if ($this->isDisabled !== null) {
@@ -269,10 +270,11 @@
         (int)$this->isApproved);
     }
 
-    if ($this->isSystemAgent) {
+    if ($this->isSystemAgent !== null) {
       $where[] = qsprintf(
         $conn_r,
-        'user.isSystemAgent = 1');
+        'user.isSystemAgent = %d',
+        (int)$this->isSystemAgent);
     }
 
     if (strlen($this->nameLike)) {
Index: src/applications/people/query/PhabricatorPeopleSearchEngine.php
===================================================================
--- src/applications/people/query/PhabricatorPeopleSearchEngine.php
+++ src/applications/people/query/PhabricatorPeopleSearchEngine.php
@@ -20,12 +20,20 @@
 
     $saved->setParameter('usernames', $request->getStrList('usernames'));
     $saved->setParameter('nameLike', $request->getStr('nameLike'));
-    $saved->setParameter('isAdmin', $request->getStr('isAdmin'));
-    $saved->setParameter('isDisabled', $request->getStr('isDisabled'));
-    $saved->setParameter('isSystemAgent', $request->getStr('isSystemAgent'));
-    $saved->setParameter('needsApproval', $request->getStr('needsApproval'));
     $saved->setParameter('createdStart', $request->getStr('createdStart'));
     $saved->setParameter('createdEnd', $request->getStr('createdEnd'));
+    $saved->setParameter(
+      'isAdmin',
+      $this->readBoolFromRequest($request, 'isAdmin'));
+    $saved->setParameter(
+      'isDisabled',
+      $this->readBoolFromRequest($request, 'isDisabled'));
+    $saved->setParameter(
+      'isSystemAgent',
+      $this->readBoolFromRequest($request, 'isSystemAgent'));
+    $saved->setParameter(
+      'needsApproval',
+      $this->readBoolFromRequest($request, 'needsApproval'));
 
     $this->readCustomFieldsFromRequest($request, $saved);
 
@@ -65,24 +73,21 @@
     $is_disabled = $saved->getParameter('isDisabled');
     $is_system_agent = $saved->getParameter('isSystemAgent');
     $needs_approval = $saved->getParameter('needsApproval');
-    $no_disabled = $saved->getParameter('noDisabled');
 
-    if ($is_admin) {
-      $query->withIsAdmin(true);
+    if ($is_admin !== null) {
+      $query->withIsAdmin($is_admin);
     }
 
-    if ($is_disabled) {
-      $query->withIsDisabled(true);
-    } else if ($no_disabled) {
-      $query->withIsDisabled(false);
+    if ($is_disabled !== null) {
+      $query->withIsDisabled($is_disabled);
     }
 
-    if ($is_system_agent) {
-      $query->withIsSystemAgent(true);
+    if ($is_system_agent !== null) {
+      $query->withIsSystemAgent($is_system_agent);
     }
 
-    if ($needs_approval) {
-      $query->withIsApproved(false);
+    if ($needs_approval !== null) {
+      $query->withIsApproved(!$needs_approval);
     }
 
     $start = $this->parseDateTime($saved->getParameter('createdStart'));
@@ -125,28 +130,49 @@
           ->setLabel(pht('Name Contains'))
           ->setValue($like))
       ->appendChild(
-        id(new AphrontFormCheckboxControl())
-          ->setLabel('Role')
-          ->addCheckbox(
-            'isAdmin',
-            1,
-            pht('Show only administrators.'),
-            $is_admin)
-          ->addCheckbox(
-            'isDisabled',
-            1,
-            pht('Show only disabled users.'),
-            $is_disabled)
-          ->addCheckbox(
-            'isSystemAgent',
-            1,
-            pht('Show only bots.'),
-            $is_system_agent)
-          ->addCheckbox(
-            'needsApproval',
-            1,
-            pht('Show only users who need approval.'),
-            $needs_approval));
+        id(new AphrontFormSelectControl())
+          ->setLabel(pht('Administrators'))
+          ->setName('isAdmin')
+          ->setValue($this->getBoolFromQuery($saved, 'isAdmin'))
+          ->setOptions(
+            array(
+              '' => pht('Show all'),
+              'true' => pht('Show only Administrators'),
+              'false' => pht('Show users that are not Administrators')
+            )))
+      ->appendChild(
+        id(new AphrontFormSelectControl())
+          ->setLabel(pht('Disabled Users'))
+          ->setName('isDisabled')
+          ->setValue($this->getBoolFromQuery($saved, 'isDisabled'))
+          ->setOptions(
+            array(
+              '' => pht('Show all'),
+              'true' => pht('Show only disabled users'),
+              'false' => pht('Show users that are not disabled')
+            )))
+      ->appendChild(
+        id(new AphrontFormSelectControl())
+          ->setLabel(pht('Bots'))
+          ->setName('isSystemAgent')
+          ->setValue($this->getBoolFromQuery($saved, 'isSystemAgent'))
+          ->setOptions(
+            array(
+              '' => pht('Show all'),
+              'true' => pht('Show only bots'),
+              'false' => pht('Show users that are not bots')
+            )))
+      ->appendChild(
+        id(new AphrontFormSelectControl())
+          ->setLabel(pht('Approved users'))
+          ->setName('needsApproval')
+          ->setValue($this->getBoolFromQuery($saved, 'needsApproval'))
+          ->setOptions(
+            array(
+              '' => pht('Show all'),
+              'false' => pht('Show approved users'),
+              'true' => pht('Show only users who need approval')
+            )));
 
     $this->appendCustomFieldsToForm($form, $saved);