How do I update upgrade pip itself from inside my virtual environment

Question

I'm able to update pip-managed packages, but how do I update pip itself? According to pip --version, I currently have pip 1.1 installed in my virtualenv and I want to update to the latest version.

What's the command for that? Do I need to use distribute or is there a native pip or virtualenv command? I've already tried pip update and pip update pip with no success.