I have some artwork against a solid white background in Illustrator. I saved as a .PNG with the transparency option turned on though when imported into AE the white background displays.
I also tried importing the artwork as a .AI file and the background also displays. I am using CC2015. What do I need to do?
Without specific details about your artwork nobody can tell you much. It simply sounds like you are using blending modes or other transparency trickery which of course will flatten the artwork to retain the appearance. this has nothing to do with AE, it's how AI works. Yopu may have to forego such stuff in favor of being able to import it into AE with everything intact and then re-create it using AE's own blending options, opacity and channel operations.
Are you still facing this problem? If not, let us know how you solved it. If so, please let us know so we can assist you further.