diff --git a/CHANGES b/CHANGES
index cb7b751e..83c1f4fe 100644
--- a/CHANGES
+++ b/CHANGES
@@ -153,7 +153,7 @@ Released on June 28th 2011, codename Grappa
 
 - Added :meth:`~flask.Flask.make_default_options_response`
   which can be used by subclasses to alter the default
-  behaviour for `OPTIONS` responses.
+  behavior for `OPTIONS` responses.
 - Unbound locals now raise a proper :exc:`RuntimeError` instead
   of an :exc:`AttributeError`.
 - Mimetype guessing and etag support based on file objects is now
@@ -163,7 +163,7 @@ Released on June 28th 2011, codename Grappa
 - Static file handling for modules now requires the name of the
   static folder to be supplied explicitly.  The previous autodetection
   was not reliable and caused issues on Google's App Engine.  Until
-  1.0 the old behaviour will continue to work but issue dependency
+  1.0 the old behavior will continue to work but issue dependency
   warnings.
 - fixed a problem for Flask to run on jython.
 - added a `PROPAGATE_EXCEPTIONS` configuration variable that can be
@@ -281,14 +281,14 @@ Released on July 6th 2010, codename Calvados
   the session cookie cross-subdomain wide.
 - autoescaping is no longer active for all templates.  Instead it
   is only active for ``.html``, ``.htm``, ``.xml`` and ``.xhtml``.
-  Inside templates this behaviour can be changed with the
+  Inside templates this behavior can be changed with the
   ``autoescape`` tag.
 - refactored Flask internally.  It now consists of more than a
   single file.
 - :func:`flask.send_file` now emits etags and has the ability to
   do conditional responses builtin.
 - (temporarily) dropped support for zipped applications.  This was a
-  rarely used feature and led to some confusing behaviour.
+  rarely used feature and led to some confusing behavior.
 - added support for per-package template and static-file directories.
 - removed support for `create_jinja_loader` which is no longer used
   in 0.5 due to the improved module support.
diff --git a/docs/design.rst b/docs/design.rst
index 6ca363a6..cc247f3b 100644
--- a/docs/design.rst
+++ b/docs/design.rst
@@ -48,7 +48,7 @@ allocated will be freed again.
 
 Another thing that becomes possible when you have an explicit object lying
 around in your code is that you can subclass the base class
-(:class:`~flask.Flask`) to alter specific behaviour.  This would not be
+(:class:`~flask.Flask`) to alter specific behavior.  This would not be
 possible without hacks if the object were created ahead of time for you
 based on a class that is not exposed to you.
 
diff --git a/docs/extensiondev.rst b/docs/extensiondev.rst
index 86c7c721..59ca76c5 100644
--- a/docs/extensiondev.rst
+++ b/docs/extensiondev.rst
@@ -40,7 +40,7 @@ that it works with multiple Flask application instances at once.  This is
 a requirement because many people will use patterns like the
 :ref:`app-factories` pattern to create their application as needed to aid
 unittests and to support multiple configurations.  Because of that it is
-crucial that your application supports that kind of behaviour.
+crucial that your application supports that kind of behavior.
 
 Most importantly the extension must be shipped with a `setup.py` file and
 registered on PyPI.  Also the development checkout link should work so
@@ -145,7 +145,7 @@ initialization functions:
 classes:
 
     Classes work mostly like initialization functions but can later be
-    used to further change the behaviour.  For an example look at how the
+    used to further change the behavior.  For an example look at how the
     `OAuth extension`_ works: there is an `OAuth` object that provides
     some helper functions like `OAuth.remote_app` to create a reference to
     a remote application that uses OAuth.
diff --git a/docs/htmlfaq.rst b/docs/htmlfaq.rst
index 1da25f3d..b16f4cd5 100644
--- a/docs/htmlfaq.rst
+++ b/docs/htmlfaq.rst
@@ -52,7 +52,7 @@ Development of the HTML5 specification was started in 2004 under the name
 "Web Applications 1.0" by the Web Hypertext Application Technology Working
 Group, or WHATWG (which was formed by the major browser vendors Apple,
 Mozilla, and Opera) with the goal of writing a new and improved HTML
-specification, based on existing browser behaviour instead of unrealistic
+specification, based on existing browser behavior instead of unrealistic
 and backwards-incompatible specifications.
 
 For example, in HTML4 ``<title/Hello/`` theoretically parses exactly the
diff --git a/docs/patterns/jquery.rst b/docs/patterns/jquery.rst
index f3c46e39..72e401fc 100644
--- a/docs/patterns/jquery.rst
+++ b/docs/patterns/jquery.rst
@@ -153,7 +153,7 @@ explanation of the little bit of code above:
 2. ``$('selector')`` selects an element and lets you operate on it.
 3. ``element.bind('event', func)`` specifies a function that should run
    when the user clicked on the element.  If that function returns
-   `false`, the default behaviour will not kick in (in this case, navigate
+   `false`, the default behavior will not kick in (in this case, navigate
    to the `#` URL).
 4. ``$.getJSON(url, data, func)`` sends a `GET` request to `url` and will
    send the contents of the `data` object as query parameters.  Once the
diff --git a/docs/patterns/mongokit.rst b/docs/patterns/mongokit.rst
index b50cf456..ae840bca 100644
--- a/docs/patterns/mongokit.rst
+++ b/docs/patterns/mongokit.rst
@@ -17,7 +17,7 @@ here:
 Declarative
 -----------
 
-The default behaviour of MongoKit is the declarative one that is based on
+The default behavior of MongoKit is the declarative one that is based on
 common ideas from Django or the SQLAlchemy declarative extension.
 
 Here an example `app.py` module for your application::
diff --git a/docs/quickstart.rst b/docs/quickstart.rst
index daaecb23..46290d0b 100644
--- a/docs/quickstart.rst
+++ b/docs/quickstart.rst
@@ -166,7 +166,7 @@ The following converters exist:
 `path`      like the default but also accepts slashes
 =========== ===========================================
 
-.. admonition:: Unique URLs / Redirection Behaviour
+.. admonition:: Unique URLs / Redirection Behavior
 
    Flask's URL rules are based on Werkzeug's routing module.  The idea
    behind that module is to ensure beautiful and unique URLs based on
diff --git a/docs/templating.rst b/docs/templating.rst
index d4878cdb..8ecf5332 100644
--- a/docs/templating.rst
+++ b/docs/templating.rst
@@ -63,7 +63,7 @@ by default:
 
    The :func:`flask.get_flashed_messages` function.
 
-.. admonition:: The Jinja Context Behaviour
+.. admonition:: The Jinja Context Behavior
 
    These variables are added to the context of variables, they are not
    global variables.  The difference is that by default these will not
diff --git a/flask/app.py b/flask/app.py
index 8460f476..4c00c36b 100644
--- a/flask/app.py
+++ b/flask/app.py
@@ -1360,7 +1360,7 @@ class Flask(_PackageBoundObject):
     def make_default_options_response(self):
         """This method is called to create the default `OPTIONS` response.
         This can be changed through subclassing to change the default
-        behaviour of `OPTIONS` responses.
+        behavior of `OPTIONS` responses.
 
         .. versionadded:: 0.7
         """
diff --git a/flask/helpers.py b/flask/helpers.py
index 1be2daf7..238d7df7 100644
--- a/flask/helpers.py
+++ b/flask/helpers.py
@@ -60,7 +60,7 @@ def _assert_have_json():
         raise RuntimeError('simplejson not installed')
 
 
-# figure out if simplejson escapes slashes.  This behaviour was changed
+# figure out if simplejson escapes slashes.  This behavior was changed
 # from one version to another without reason.
 if not json_available or '\\/' not in json.dumps('/'):
 
@@ -121,7 +121,7 @@ def jsonify(*args, **kwargs):
 
     .. versionadded:: 0.9
         If the ``padded`` argument is true, the JSON object will be padded
-        for JSONP calls and the response mimetype will be changed to 
+        for JSONP calls and the response mimetype will be changed to
         ``application/javascript``. By default, the request arguments ``callback``
         and ``jsonp`` will be used as the name for the callback function.
         This will work with jQuery and most other JavaScript libraries
@@ -387,7 +387,7 @@ def send_file(filename_or_fp, mimetype=None, as_attachment=False,
 
     .. versionadded:: 0.5
        The `add_etags`, `cache_timeout` and `conditional` parameters were
-       added.  The default behaviour is now to attach etags.
+       added.  The default behavior is now to attach etags.
 
     .. versionchanged:: 0.7
        mimetype guessing and etag support for file objects was
@@ -422,7 +422,7 @@ def send_file(filename_or_fp, mimetype=None, as_attachment=False,
         file = filename_or_fp
         filename = getattr(file, 'name', None)
 
-        # XXX: this behaviour is now deprecated because it was unreliable.
+        # XXX: this behavior is now deprecated because it was unreliable.
         # removed in Flask 1.0
         if not attachment_filename and not mimetype \
            and isinstance(filename, basestring):
@@ -433,7 +433,7 @@ def send_file(filename_or_fp, mimetype=None, as_attachment=False,
         if add_etags:
             warn(DeprecationWarning('In future flask releases etags will no '
                 'longer be generated for file objects passed to the send_file '
-                'function because this behaviour was unreliable.  Pass '
+                'function because this behavior was unreliable.  Pass '
                 'filenames instead if possible, otherwise attach an etag '
                 'yourself based on another value'), stacklevel=2)