Mixing ASP and ASP.NET files together

I have a client that has a website that is 100% ASP. We are talking about adding 3 new pages that would be ASP.NET-based. Is there any problem with running ASP and ASP.NET pages together on the same website?

I'm trying to find this out before I get involved and find out that it's a huge undertaking. Anyone with past experience, I'd love to hear your story.

Thanks!Aspx can run with asp pages side by side in same web site. One thing is not easy to do is to share Session state between aspx and asp pages.
Thanks Jimmym. I appreciate the feedback.
Set the AspCompat attribute to True in the aspx pages, page directive then add the asp code in your aspx pages.

You can then use the functionality of server controls etc to further enhance the application.
Great tip!!! Thanks a bunch Midi25.