diff --git a/lib/fn/btr_user.php b/lib/fn/btr_user.php
index 98ff818..d4aa7f0 100644
--- a/lib/fn/btr_user.php
+++ b/lib/fn/btr_user.php
@@ -52,3 +52,10 @@ function btr_user_set($data) {
 
   $_SESSION['btrClient']['btr_user'] = $btr_user;
 }
+
+/**
+ * Remove btr_user from the session.
+ */
+function btr_user_expire() {
+  unset($_SESSION['btrClient']['btr_user']);
+}
diff --git a/project/callback/dashboard.inc b/project/callback/dashboard.inc
index f190f27..ce59fb5 100644
--- a/project/callback/dashboard.inc
+++ b/project/callback/dashboard.inc
@@ -8,7 +8,9 @@
  * Menu callback for 'btr/project/%/%/%/dashboard'
  */
 function btrProject_dashboard($origin, $project, $lng) {
-  $output = [
+  $output[] = drupal_get_form('btrProject_subscribe_form', $origin, $project);
+
+  $output[] = [
     'statistics' => [
       '#prefix' => '<div class="col-sm-4">',
       bcl::get_block('btrProject', 'statistics'),
@@ -28,3 +30,80 @@ function btrProject_dashboard($origin, $project, $lng) {
 
   return $output;
 }
+
+/**
+ * Form callback for: btrProject_subscribe_form
+ */
+function btrProject_subscribe_form($form, &$form_state, $origin, $project) {
+  $subscribed = _btrProject_user_subscribed($origin, $project);
+  $form = [
+    'origin' => [
+      '#type' => 'hidden',
+      '#value' => $origin,
+    ],
+    'project' => [
+      '#type' => 'hidden',
+      '#value' => $project,
+    ],
+    'subscribe' => [
+      '#value' => t('Subscribe'),
+      '#type' => 'submit',
+      '#attributes' => ['class' => ['btn-primary']],
+      '#access' => !$subscribed,
+    ],
+    'unsubscribe' => [
+      '#value' => t('Unsubscribe'),
+      '#type' => 'submit',
+      '#attributes' => ['class' => ['btn-primary']],
+      '#access' => $subscribed,
+    ],
+  ];
+
+  return $form;
+}
+
+/**
+ * Return TRUE if the user is subscribed to the given project.
+ */
+function _btrProject_user_subscribed($origin, $project) {
+  if (!bcl::user_is_authenticated()) return FALSE;
+
+  // Check the given project on the list of preferred_projects.
+  $btr_user = bcl::btr_user_get();
+  if (!isset($btr_user['preferred_projects']))  return FALSE;
+  return in_array("$origin/$project", $btr_user['preferred_projects']);
+}
+
+/**
+ * Submit callback for the form: btrProject_subscribe_form
+ */
+function btrProject_subscribe_form_submit($form, &$form_state) {
+  // If user is not authenticated, redirect to login first.
+  if (!bcl::user_is_authenticated()) {
+    bcl::user_authenticate($form_state, $redirection = ($form===NULL));
+    return;
+  }
+
+  // Get the parameters.
+  $values = $form_state['values'];
+  $operation = $values['op'];
+  $origin = $values['origin'];
+  $project = $values['project'];
+
+  $btr = wsclient_service_load('btr');
+  if ($operation == t('Subscribe')) {
+    // Subscribe to the project.
+    $btr->subscribe(['origin' => $origin, 'project' => $project]);
+    $msg = t("Subscribed to project '!project'.", ['!project' => "$origin/$project"]);
+  }
+  elseif ($operation == t('Unsubscribe')) {
+    // Unsubscribe from the project.
+    $btr->unsubscribe(['origin' => $origin, 'project' => $project]);
+    $msg = t("Unsubscribed from project '!project'.", ['!project' => "$origin/$project"]);
+  }
+  drupal_set_message($msg);
+
+  // Expire from cache the btr_user, so that it can be
+  // refreshed with the latest values.
+  bcl::btr_user_expire();
+}
diff --git a/services/authenticated.inc b/services/authenticated.inc
index c948b9f..6168473 100644
--- a/services/authenticated.inc
+++ b/services/authenticated.inc
@@ -94,6 +94,9 @@ function _btrClientWS_authenticated_translations() {
  */
 function _btrClientWS_authenticated_projects() {
   $post_operations = array(
+    'subscribe' => 'project/subscribe',
+    'unsubscribe' => 'project/unsubscribe',
+    'subscriptions' => 'project/subscriptions',
     'export_projects' => 'project/export',
     'add_string' => 'project/add_string',
     'del_string' => 'project/del_string',