Posts from multiple categories on one page

Hello…

I’m looking to display posts from categories 1 and 2 on the same space – be it a page, or whatever. My slugs are ‘primary’ and ‘secondary’, and this works to display from only primary:

http://domain.com/category/primary/

I’d like to have posts from both primary and secondary displayed. Is there a built-in way to do this, or can I create a page that will do this?

Your help is appreciated. Thanks!

dan