diff --git a/Doc/using/cmdline.rst b/Doc/using/cmdline.rst
index b61df8a..0e75ce5 100644
--- a/Doc/using/cmdline.rst
+++ b/Doc/using/cmdline.rst
@@ -99,6 +99,11 @@ source.
    full path to the module file (while the module file is being located, the
    first element will be set to ``"-m"``). As with the :option:`-c` option,
    the current directory will be added to the start of :data:`sys.path`.
+   :option:`-I` option can  be used to run the script in isolated mode where
+   :data:`sys.path` contains neither the script's directory nor the user's
+   site-packages directory. All :envvar:`PYTHON*` environment variables are
+   ignored, too.
+

    Many standard library modules contain code that is invoked on their execution
    as a script.  An example is the :mod:`timeit` module::
@@ -148,5 +153,10 @@ source.
    added to the start of :data:`sys.path` and the ``__main__.py`` file in
    that location is executed as the :mod:`__main__` module.

+   :option:`-I` option can  be used to run the script in isolated mode where
+   :data:`sys.path` contains neither the script's directory nor the user's
+   site-packages directory. All :envvar:`PYTHON*` environment variables are
+   ignored, too.
+
    .. seealso::
       :func:`runpy.run_path`
          Equivalent functionality directly available to Python code