robots noindex on an iframe page

What would this do?

[dataguy]

There is a web site which is iframing some of my content, and it is ranking very well. I was wondering if I added a meta robots nofollow tag to this page how it would effect the pages which are displaying my content.

Anyone with experience with this?

[goodroi]

i've done that in the past to deal with some duplicate content issues, worked for me just fine