Read the back of the immigration and declaration form (form I-94...I think) before going through U.S. customs with prescription meds. If I remember correctly it does mention something about declaring controlled substances obtained abroad. I think it even says controlled substances are prohibited that are obtained overseas. I could be wrong, but I would do some research on the web.

Definitely don't hide them...I just got back from Asia a week after the U.S. starting bombing Iraq and customs went through ALL my stuff.

Take care.

-EW