diff --git a/lib/class-sendgrid-nlvx.php b/lib/class-sendgrid-nlvx.php
index 8d99f7d..0605a1a 100644
--- a/lib/class-sendgrid-nlvx.php
+++ b/lib/class-sendgrid-nlvx.php
@@ -79,10 +79,11 @@ public static function get_all_lists()
    * @param   string $email          The email of the recipient
    * @param   string $first_name     The first name of the recipient
    * @param   string $last_name      The last name of the recipient
+   * @param   array  $custom_fields  Custom field data
    *
    * @return  mixed   The recipient ID if successful, false otherwise.
    */
-  public static function add_recipient($email, $first_name = '', $last_name = '')
+  public static function add_recipient($email, $first_name = '', $last_name = '', array $custom_fields = array())
   {
     $auth = Sendgrid_NLVX::get_auth_header_value();
 
@@ -108,6 +109,10 @@ public static function add_recipient($email, $first_name = '', $last_name = '')
     if ( '' != $last_name ) {
       $contact['last_name'] = $last_name;
     }
+    
+    foreach ( $custom_fields as $field => $value ) {
+      $contact[$field] = $value;
+    }
 
     $req_body = json_encode(array($contact));
     $args['body'] = $req_body;
@@ -191,4 +196,4 @@ public static function create_and_add_recipient_to_list($email, $first_name = ''
 
     return Sendgrid_NLVX::add_recipient_to_list($recipient_id, $list_id);
   }
-}
\ No newline at end of file
+}