I have a 2001 Chevy Impala and while driving to work one morning I flipped the dimmer switch to put my lights on low beam and Both lights went out. Now the low beams will not come but high beams will. What could be the cause of this problem? Thank you for any help you can give me.

could be the switch itself, you check all the fuses?

I had the same problem in my car. Turned out to be a bad dimmer switch. After it was replaced, it worked perfect, and that was over a year ago. Its a common problem in a few GM cars.