diff --git a/cookbook/map.rst.inc b/cookbook/map.rst.inc
index 99498b50a7a..49a65cf8462 100644
--- a/cookbook/map.rst.inc
+++ b/cookbook/map.rst.inc
@@ -166,6 +166,7 @@
   * :doc:`/cookbook/session/sessions_directory`
   * :doc:`/cookbook/session/php_bridge`
   * (configuration) :doc:`/cookbook/configuration/pdo_session_storage`
+  * :doc:`/cookbook/session/avoid_session_start`
 
 * **symfony1**
 
diff --git a/cookbook/session/avoid_session_start.rst b/cookbook/session/avoid_session_start.rst
new file mode 100644
index 00000000000..8736f484ad6
--- /dev/null
+++ b/cookbook/session/avoid_session_start.rst
@@ -0,0 +1,38 @@
+.. index::
+    single: Sessions, cookies
+
+Avoid Starting Sessions for Anonymous Users
+===========================================
+
+Sessions are automatically started whenever you read, write or even check for the
+existence of data in the session. This means that if you need to avoid creating
+a session cookie for some users, it can be difficult: you must *completely* avoid
+accessing the session.
+
+For example, one common problem in this situation involves checking for flash
+messages, which are stored in the session. The following code would guarantee
+that a session is *always* started:
+
+.. code-block:: html+jinja
+
+    {% for flashMessage in app.session.flashbag.get('notice') %}
+        <div class="flash-notice">
+            {{ flashMessage }}
+        </div>
+    {% endfor %}
+
+Even if the user is not logged in and even if you haven't created any flash message,
+just calling the ``get()`` (or even ``has()``) method of the ``flashbag`` will
+start a session. This may hurt your application performance because all users will
+receive a session cookie. To avoid this behavior, add a check before trying to
+access the flash messages:
+
+.. code-block:: html+jinja
+
+    {% if app.request.hasPreviousSession %}
+        {% for flashMessage in app.session.flashbag.get('notice') %}
+            <div class="flash-notice">
+                {{ flashMessage }}
+            </div>
+        {% endfor %}
+    {% endif %}
diff --git a/cookbook/session/index.rst b/cookbook/session/index.rst
index 536ad02c3d8..0420126b48e 100644
--- a/cookbook/session/index.rst
+++ b/cookbook/session/index.rst
@@ -7,4 +7,5 @@ Sessions
     proxy_examples
     locale_sticky_session
     sessions_directory
-    php_bridge
\ No newline at end of file
+    php_bridge
+    avoid_session_start
\ No newline at end of file