We need a little more info. Take a test lite (I do not prefer a meter) and check for juice at the wire (not bulb) side of the bulb connections. If you have power there, you clean the bulb bases and contacts, but it is unlikely that all those connections would go out at once. If no juice, check the light switch terminal and the connections to it. You can do a quicck/dirty check for ground issues by cleaning the brass base of one bulb and leaving it in place jump from the clean spot all the way to the batt ground. Get back here after these tests if the problem is not identified.
Bob