diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -549,6 +549,7 @@
     'DifferentialRevisionRequiredActionResultBucket' => 'applications/differential/query/DifferentialRevisionRequiredActionResultBucket.php',
     'DifferentialRevisionResultBucket' => 'applications/differential/query/DifferentialRevisionResultBucket.php',
     'DifferentialRevisionReviewersHeraldField' => 'applications/differential/herald/DifferentialRevisionReviewersHeraldField.php',
+    'DifferentialRevisionReviewersTransaction' => 'applications/differential/xaction/DifferentialRevisionReviewersTransaction.php',
     'DifferentialRevisionSearchConduitAPIMethod' => 'applications/differential/conduit/DifferentialRevisionSearchConduitAPIMethod.php',
     'DifferentialRevisionSearchEngine' => 'applications/differential/query/DifferentialRevisionSearchEngine.php',
     'DifferentialRevisionStatus' => 'applications/differential/constants/DifferentialRevisionStatus.php',
@@ -5202,6 +5203,7 @@
     'DifferentialRevisionRequiredActionResultBucket' => 'DifferentialRevisionResultBucket',
     'DifferentialRevisionResultBucket' => 'PhabricatorSearchResultBucket',
     'DifferentialRevisionReviewersHeraldField' => 'DifferentialRevisionHeraldField',
+    'DifferentialRevisionReviewersTransaction' => 'DifferentialRevisionTransactionType',
     'DifferentialRevisionSearchConduitAPIMethod' => 'PhabricatorSearchEngineAPIMethod',
     'DifferentialRevisionSearchEngine' => 'PhabricatorApplicationSearchEngine',
     'DifferentialRevisionStatus' => 'Phobject',
diff --git a/src/applications/differential/editor/DifferentialRevisionEditEngine.php b/src/applications/differential/editor/DifferentialRevisionEditEngine.php
--- a/src/applications/differential/editor/DifferentialRevisionEditEngine.php
+++ b/src/applications/differential/editor/DifferentialRevisionEditEngine.php
@@ -32,7 +32,8 @@
   }
 
   protected function newObjectQuery() {
-    return new DifferentialRevisionQuery();
+    return id(new DifferentialRevisionQuery())
+      ->needReviewerStatus(true);
   }
 
   protected function getObjectCreateTitleText($object) {
@@ -104,6 +105,18 @@
     }
 
     $fields[] = id(new PhabricatorDatasourceEditField())
+      ->setKey('reviewerPHIDs')
+      ->setLabel(pht('Reviewers'))
+      ->setDatasource(new DifferentialReviewerDatasource())
+      ->setUseEdgeTransactions(true)
+      ->setTransactionType(
+        DifferentialRevisionReviewersTransaction::TRANSACTIONTYPE)
+      ->setDescription(pht('Reviewers for this revision.'))
+      ->setConduitDescription(pht('Change the reviewers for this revision.'))
+      ->setConduitTypeDescription(pht('New reviewers.'))
+      ->setValue($object->getReviewerPHIDsForEdit());
+
+    $fields[] = id(new PhabricatorDatasourceEditField())
       ->setKey('repositoryPHID')
       ->setLabel(pht('Repository'))
       ->setDatasource(new DiffusionRepositoryDatasource())
diff --git a/src/applications/differential/storage/DifferentialRevision.php b/src/applications/differential/storage/DifferentialRevision.php
--- a/src/applications/differential/storage/DifferentialRevision.php
+++ b/src/applications/differential/storage/DifferentialRevision.php
@@ -409,6 +409,24 @@
     return $this;
   }
 
+  public function getReviewerPHIDsForEdit() {
+    $reviewers = $this->getReviewerStatus();
+
+    $status_blocking = DifferentialReviewerStatus::STATUS_BLOCKING;
+
+    $value = array();
+    foreach ($reviewers as $reviewer) {
+      $phid = $reviewer->getReviewerPHID();
+      if ($reviewer->getStatus() == $status_blocking) {
+        $value[] = 'blocking('.$phid.')';
+      } else {
+        $value[] = $phid;
+      }
+    }
+
+    return $value;
+  }
+
   public function getRepository() {
     return $this->assertAttached($this->repository);
   }
diff --git a/src/applications/differential/xaction/DifferentialRevisionReviewersTransaction.php b/src/applications/differential/xaction/DifferentialRevisionReviewersTransaction.php
new file mode 100644
--- /dev/null
+++ b/src/applications/differential/xaction/DifferentialRevisionReviewersTransaction.php
@@ -0,0 +1,350 @@
+<?php
+
+final class DifferentialRevisionReviewersTransaction
+  extends DifferentialRevisionTransactionType {
+
+  const TRANSACTIONTYPE = 'differential.revision.reviewers';
+
+  public function generateOldValue($object) {
+    $reviewers = $object->getReviewerStatus();
+    $reviewers = mpull($reviewers, 'getStatus', 'getReviewerPHID');
+    return $reviewers;
+  }
+
+  public function generateNewValue($object, $value) {
+    $actor = $this->getActor();
+
+    $datasource = id(new DifferentialBlockingReviewerDatasource())
+      ->setViewer($actor);
+
+    $reviewers = $this->generateOldValue($object);
+
+    // First, remove any reviewers we're getting rid of.
+    $rem = idx($value, '-', array());
+    $rem = $datasource->evaluateTokens($rem);
+    foreach ($rem as $phid) {
+      unset($reviewers[$phid]);
+    }
+
+    $add = idx($value, '+', array());
+    $add = $datasource->evaluateTokens($add);
+    $add_map = array();
+    foreach ($add as $spec) {
+      if (!is_array($spec)) {
+        $phid = $spec;
+        $status = DifferentialReviewerStatus::STATUS_ADDED;
+      } else {
+        $phid = $spec['phid'];
+        $status = $spec['type'];
+      }
+
+      $add_map[$phid] = $status;
+    }
+
+    $set = idx($value, '=', null);
+    if ($set !== null) {
+      $set = $datasource->evaluateTokens($set);
+      foreach ($set as $spec) {
+        if (!is_array($spec)) {
+          $phid = $spec;
+          $status = DifferentialReviewerStatus::STATUS_ADDED;
+        } else {
+          $phid = $spec['phid'];
+          $status = $spec['type'];
+        }
+
+        $add_map[$phid] = $status;
+      }
+
+      // We treat setting reviewers as though they were being added to an
+      // empty list, so we can share more code between pathways.
+      $reviewers = array();
+    }
+
+    $status_blocking = DifferentialReviewerStatus::STATUS_BLOCKING;
+    foreach ($add_map as $phid => $new_status) {
+      $old_status = idx($reviewers, $phid);
+
+      // If we have an old status and this didn't make the reviewer blocking
+      // or nonblocking, just retain the old status. This makes sure we don't
+      // throw away rejects, accepts, etc.
+      if ($old_status) {
+        $was_blocking = ($old_status == $status_blocking);
+        $now_blocking = ($new_status == $status_blocking);
+
+        $is_block = ($now_blocking && !$was_blocking);
+        $is_unblock = (!$now_blocking && $was_blocking);
+
+        if (!$is_block && !$is_unblock) {
+          continue;
+        }
+      }
+
+      $reviewers[$phid] = $new_status;
+    }
+
+    return $reviewers;
+  }
+
+  public function applyExternalEffects($object, $value) {
+    $src_phid = $object->getPHID();
+
+    $old = $this->generateOldValue($object);
+    $new = $value;
+    $edge_type = DifferentialRevisionHasReviewerEdgeType::EDGECONST;
+
+    $editor = new PhabricatorEdgeEditor();
+
+    $rem = array_diff_key($old, $new);
+    foreach ($rem as $dst_phid => $status) {
+      $editor->removeEdge($src_phid, $edge_type, $dst_phid);
+    }
+
+    foreach ($new as $dst_phid => $status) {
+      $old_status = idx($old, $dst_phid);
+      if ($old_status === $status) {
+        continue;
+      }
+
+      $data = array(
+        'data' => array(
+          'status' => $status,
+
+          // TODO: This seemes like it's buggy before the Modular Transactions
+          // changes. Figure out what's going on here? We don't have a very
+          // clean way to get the active diff ID right now.
+          'diffID' => null,
+        ),
+      );
+
+      $editor->addEdge($src_phid, $edge_type, $dst_phid, $data);
+    }
+
+    $editor->save();
+  }
+
+  public function getTitle() {
+    return $this->renderReviewerEditTitle(false);
+  }
+
+  public function getTitleForFeed() {
+    return $this->renderReviewerEditTitle(true);
+  }
+
+  private function renderReviewerEditTitle($is_feed) {
+    $old = $this->getOldValue();
+    $new = $this->getNewValue();
+
+    $rem = array_diff_key($old, $new);
+    $add = array_diff_key($new, $old);
+    $rem_phids = array_keys($rem);
+    $add_phids = array_keys($add);
+    $total_count = count($rem) + count($add);
+
+    $parts = array();
+
+    if ($rem && $add) {
+      if ($is_feed) {
+        $parts[] = pht(
+          '%s edited %s reviewer(s) for %s, added %s: %s; removed %s: %s.',
+          $this->renderAuthor(),
+          new PhutilNumber($total_count),
+          $this->renderObject(),
+          phutil_count($add_phids),
+          $this->renderHandleList($add_phids),
+          phutil_count($rem_phids),
+          $this->renderHandleList($rem_phids));
+      } else {
+        $parts[] = pht(
+          '%s edited %s reviewer(s), added %s: %s; removed %s: %s.',
+          $this->renderAuthor(),
+          new PhutilNumber($total_count),
+          phutil_count($add_phids),
+          $this->renderHandleList($add_phids),
+          phutil_count($rem_phids),
+          $this->renderHandleList($rem_phids));
+      }
+    } else if ($add) {
+      if ($is_feed) {
+        $parts[] = pht(
+          '%s added %s reviewer(s) for %s: %s.',
+          $this->renderAuthor(),
+          phutil_count($add_phids),
+          $this->renderObject(),
+          $this->renderHandleList($add_phids));
+      } else {
+        $parts[] = pht(
+          '%s added %s reviewer(s): %s.',
+          $this->renderAuthor(),
+          phutil_count($add_phids),
+          $this->renderHandleList($add_phids));
+      }
+    } else if ($rem) {
+      if ($is_feed) {
+        $parts[] = pht(
+          '%s removed %s reviewer(s) for %s: %s.',
+          $this->renderAuthor(),
+          phutil_count($rem_phids),
+          $this->renderObject(),
+          $this->renderHandleList($rem_phids));
+      } else {
+        $parts[] = pht(
+          '%s removed %s reviewer(s): %s.',
+          $this->renderAuthor(),
+          phutil_count($rem_phids),
+          $this->renderHandleList($rem_phids));
+      }
+    }
+
+    $status_blocking = DifferentialReviewerStatus::STATUS_BLOCKING;
+    $blocks = array();
+    $unblocks = array();
+    foreach ($new as $phid => $new_status) {
+      $old_status = idx($old, $phid);
+      if (!$old_status) {
+        continue;
+      }
+
+      $was_blocking = ($old_status == $status_blocking);
+      $now_blocking = ($new_status == $status_blocking);
+
+      $is_block = ($now_blocking && !$was_blocking);
+      $is_unblock = (!$now_blocking && $was_blocking);
+
+      if ($is_block) {
+        $blocks[] = $phid;
+      }
+      if ($is_unblock) {
+        $unblocks[] = $phid;
+      }
+    }
+
+    $total_count = count($blocks) + count($unblocks);
+
+    if ($blocks && $unblocks) {
+      if ($is_feed) {
+        $parts[] = pht(
+          '%s changed %s blocking reviewer(s) for %s, added %s: %s; removed '.
+          '%s: %s.',
+          $this->renderAuthor(),
+          new PhutilNumber($total_count),
+          $this->renderObject(),
+          phutil_count($blocks),
+          $this->renderHandleList($blocks),
+          phutil_count($unblocks),
+          $this->renderHandleList($unblocks));
+      } else {
+        $parts[] = pht(
+          '%s changed %s blocking reviewer(s), added %s: %s; removed %s: %s.',
+          $this->renderAuthor(),
+          new PhutilNumber($total_count),
+          phutil_count($blocks),
+          $this->renderHandleList($blocks),
+          phutil_count($unblocks),
+          $this->renderHandleList($unblocks));
+      }
+    } else if ($blocks) {
+      if ($is_feed) {
+        $parts[] = pht(
+          '%s added %s blocking reviewer(s) for %s: %s.',
+          $this->renderAuthor(),
+          phutil_count($blocks),
+          $this->renderObject(),
+          $this->renderHandleList($blocks));
+      } else {
+        $parts[] = pht(
+          '%s added %s blocking reviewer(s): %s.',
+          $this->renderAuthor(),
+          phutil_count($blocks),
+          $this->renderHandleList($blocks));
+      }
+    } else if ($unblocks) {
+      if ($is_feed) {
+        $parts[] = pht(
+          '%s removed %s blocking reviewer(s) for %s: %s.',
+          $this->renderAuthor(),
+          phutil_count($unblocks),
+          $this->renderObject(),
+          $this->renderHandleList($unblocks));
+      } else {
+        $parts[] = pht(
+          '%s removed %s blocking reviewer(s): %s.',
+          $this->renderAuthor(),
+          phutil_count($unblocks),
+          $this->renderHandleList($unblocks));
+      }
+    }
+
+    if ($this->isTextMode()) {
+      return implode(' ', $parts);
+    } else {
+      return phutil_implode_html(' ', $parts);
+    }
+  }
+
+  public function validateTransactions($object, array $xactions) {
+    $actor = $this->getActor();
+    $errors = array();
+
+    $author_phid = $object->getAuthorPHID();
+    $config_self_accept_key = 'differential.allow-self-accept';
+    $allow_self_accept = PhabricatorEnv::getEnvConfig($config_self_accept_key);
+
+    $old = $this->generateOldValue($object);
+    foreach ($xactions as $xaction) {
+      $new = $this->generateNewValue($object, $xaction->getNewValue());
+
+      $add = array_diff_key($new, $old);
+      if (!$add) {
+        continue;
+      }
+
+      $objects = id(new PhabricatorObjectQuery())
+        ->setViewer($actor)
+        ->withPHIDs(array_keys($add))
+        ->execute();
+      $objects = mpull($objects, null, 'getPHID');
+
+      foreach ($add as $phid => $status) {
+        if (!isset($objects[$phid])) {
+          $errors[] = $this->newInvalidError(
+            pht(
+              'Reviewer "%s" is not a valid object.',
+              $phid),
+            $xaction);
+          continue;
+        }
+
+        switch (phid_get_type($phid)) {
+          case PhabricatorPeopleUserPHIDType::TYPECONST:
+          case PhabricatorOwnersPackagePHIDType::TYPECONST:
+          case PhabricatorProjectProjectPHIDType::TYPECONST:
+            break;
+          default:
+            $errors[] = $this->newInvalidError(
+              pht(
+                'Reviewer "%s" must be a user, a package, or a project.',
+                $phid),
+              $xaction);
+            continue 2;
+        }
+
+        // NOTE: This weird behavior around commandeering is a bit unorthodox,
+        // but this restriction is an unusual one.
+
+        $is_self = ($phid === $author_phid);
+        if ($is_self && !$allow_self_accept) {
+          if (!$xaction->getIsCommandeerSideEffect()) {
+            $errors[] = $this->newInvalidError(
+              pht('The author of a revision can not be a reviewer.'),
+              $xaction);
+            continue;
+          }
+        }
+      }
+    }
+
+    return $errors;
+  }
+
+}
diff --git a/src/applications/transactions/storage/PhabricatorModularTransactionType.php b/src/applications/transactions/storage/PhabricatorModularTransactionType.php
--- a/src/applications/transactions/storage/PhabricatorModularTransactionType.php
+++ b/src/applications/transactions/storage/PhabricatorModularTransactionType.php
@@ -277,7 +277,7 @@
     return !strlen($value);
   }
 
-  private function isTextMode() {
+  protected function isTextMode() {
     $target = $this->getStorage()->getRenderingTarget();
     return ($target == PhabricatorApplicationTransaction::TARGET_TEXT);
   }