diff --git a/src/land/engine/ArcanistGitLandEngine.php b/src/land/engine/ArcanistGitLandEngine.php
--- a/src/land/engine/ArcanistGitLandEngine.php
+++ b/src/land/engine/ArcanistGitLandEngine.php
@@ -876,6 +876,8 @@
   }
 
   protected function confirmOntoRefs(array $onto_refs) {
+    $api = $this->getRepositoryAPI();
+
     foreach ($onto_refs as $onto_ref) {
       if (!strlen($onto_ref)) {
         throw new PhutilArgumentUsageException(
@@ -886,10 +888,61 @@
       }
     }
 
-    // TODO: Check that these refs really exist in the remote? Checking the
-    // remote is expensive and users probably rarely specify "--onto" manually,
-    // but if "arc land" creates branches without prompting when you make typos
-    // that also seems questionable.
+    $markers = $api->newMarkerRefQuery()
+      ->withRemotes(array($this->getOntoRemoteRef()))
+      ->withNames($onto_refs)
+      ->execute();
+
+    $markers = mgroup($markers, 'getName');
+
+    $new_markers = array();
+    foreach ($onto_refs as $onto_ref) {
+      if (isset($markers[$onto_ref])) {
+        // Remote already has a branch with this name, so we're fine: we
+        // aren't creatinga new branch.
+        continue;
+      }
+
+      $new_markers[] = id(new ArcanistMarkerRef())
+        ->setMarkerType(ArcanistMarkerRef::TYPE_BRANCH)
+        ->setName($onto_ref);
+    }
+
+    if ($new_markers) {
+      echo tsprintf(
+        "\n%!\n%W\n\n",
+        pht('CREATE %s BRANCHE(S)', phutil_count($new_markers)),
+        pht(
+          'These %s symbol(s) do not exist in the remote. They will be '.
+          'created as new branches:',
+          phutil_count($new_markers)));
+
+      foreach ($new_markers as $new_marker) {
+        echo tsprintf('%s', $new_marker->newRefView());
+      }
+
+      echo tsprintf("\n");
+
+      $is_hold = $this->getShouldHold();
+      if ($is_hold) {
+        echo tsprintf(
+          "%?\n",
+          pht(
+            'You are using "--hold", so execution will stop before the '.
+            '%s branche(s) are actually created. You will be given '.
+            'instructions to create the branches.',
+            phutil_count($new_markers)));
+      }
+
+      $query = pht(
+        'Create %s new branche(s) in the remote?',
+        phutil_count($new_markers));
+
+      $this->getWorkflow()
+        ->getPrompt('arc.land.create')
+        ->setQuery($query)
+        ->execute();
+    }
   }
 
   protected function selectOntoRefs(array $symbols) {
@@ -1238,6 +1291,7 @@
     $api = $this->getRepositoryAPI();
     // Make sure that our "into" target is valid.
     $log = $this->getLogEngine();
+    $api = $this->getRepositoryAPI();
 
     if ($this->getIntoEmpty()) {
       // If we're running under "--into-empty", we don't have to do anything.
diff --git a/src/land/engine/ArcanistLandEngine.php b/src/land/engine/ArcanistLandEngine.php
--- a/src/land/engine/ArcanistLandEngine.php
+++ b/src/land/engine/ArcanistLandEngine.php
@@ -1569,4 +1569,9 @@
     return $command->execute();
   }
 
+  final protected function getOntoRemoteRef() {
+    return id(new ArcanistRemoteRef())
+      ->setRemoteName($this->getOntoRemote());
+  }
+
 }
diff --git a/src/land/engine/ArcanistMercurialLandEngine.php b/src/land/engine/ArcanistMercurialLandEngine.php
--- a/src/land/engine/ArcanistMercurialLandEngine.php
+++ b/src/land/engine/ArcanistMercurialLandEngine.php
@@ -270,8 +270,7 @@
       }
     }
 
-    $remote_ref = id(new ArcanistRemoteRef())
-      ->setRemoteName($this->getOntoRemote());
+    $remote_ref = $this->getOntoRemoteRef();
 
     $markers = $api->newMarkerRefQuery()
       ->withRemotes(array($remote_ref))
@@ -346,8 +345,8 @@
         "\n%!\n%W\n\n",
         pht('CREATE %s BOOKMARK(S)', phutil_count($new_markers)),
         pht(
-          'These %s symbol(s) do not exist in the remote. They will be created '.
-          'as new bookmarks:',
+          'These %s symbol(s) do not exist in the remote. They will be '.
+          'created as new bookmarks:',
           phutil_count($new_markers)));
 
 
@@ -357,6 +356,17 @@
 
       echo tsprintf("\n");
 
+      $is_hold = $this->getShouldHold();
+      if ($is_hold) {
+        echo tsprintf(
+          "%?\n",
+          pht(
+            'You are using "--hold", so execution will stop before the '.
+            '%s bookmark(s) are actually created. You will be given '.
+            'instructions to create the bookmarks.',
+            phutil_count($new_markers)));
+      }
+
       $query = pht(
         'Create %s new remote bookmark(s)?',
         phutil_count($new_markers));
diff --git a/src/repository/marker/ArcanistGitRepositoryMarkerQuery.php b/src/repository/marker/ArcanistGitRepositoryMarkerQuery.php
--- a/src/repository/marker/ArcanistGitRepositoryMarkerQuery.php
+++ b/src/repository/marker/ArcanistGitRepositoryMarkerQuery.php
@@ -122,7 +122,59 @@
   }
 
   protected function newRemoteRefMarkers(ArcanistRemoteRef $remote) {
-    throw new PhutilMethodNotImplementedException();
+    $api = $this->getRepositoryAPI();
+
+    // NOTE: Since we only care about branches today, we only list branches.
+
+    $future = $api->newFuture(
+      'ls-remote --refs %s %s',
+      $remote->getRemoteName(),
+      'refs/heads/*');
+    list($stdout) = $future->resolve();
+
+    $branch_prefix = 'refs/heads/';
+    $branch_length = strlen($branch_prefix);
+
+    $pattern = '(^(?P<hash>\S+)\t(?P<ref>\S+)\z)';
+    $markers = array();
+
+    $lines = phutil_split_lines($stdout, false);
+    foreach ($lines as $line) {
+      $matches = null;
+      $ok = preg_match($pattern, $line, $matches);
+      if (!$ok) {
+        throw new Exception(
+          pht(
+            'Failed to match "ls-remote" pattern against line "%s".',
+            $line));
+      }
+
+      $hash = $matches['hash'];
+      $ref = $matches['ref'];
+
+      if (!strncmp($ref, $branch_prefix, $branch_length)) {
+        $type = ArcanistMarkerRef::TYPE_BRANCH;
+        $name = substr($ref, $branch_length);
+      } else {
+        // For now, discard other refs.
+        continue;
+      }
+
+      $marker = id(new ArcanistMarkerRef())
+        ->setName($name)
+        ->setMarkerType($type)
+        ->setMarkerHash($hash)
+        ->setCommitHash($hash);
+
+      $commit_ref = $api->newCommitRef()
+        ->setCommitHash($hash);
+
+      $marker->attachCommitRef($commit_ref);
+
+      $markers[] = $marker;
+    }
+
+    return $markers;
   }
 
 }
diff --git a/src/xsprintf/tsprintf.php b/src/xsprintf/tsprintf.php
--- a/src/xsprintf/tsprintf.php
+++ b/src/xsprintf/tsprintf.php
@@ -51,6 +51,7 @@
     case '?':
       $value = tsprintf('<bg:green>**  ?  **</bg> %s', $value);
       $value = PhutilTerminalString::escapeStringValue($value, false);
+      $value = phutil_console_wrap($value, 6, false);
       $type = 's';
       break;
     case '>':