My 90 Nissan Sentra's brake lites recently quit working,I Ck'ed all fuses,& replaced brake pedal stop lite switch.
They still don't work.Anyone have an idea?

I'd check to see that the switch is receiving the proper voltage. If there is power to the switch then I'd do some tracing from the switch back to the lights. If you have no power reaching the the switch, do some tracing the opposite way, towards the power source.

Correct bulbs? Are they wired together in a circuit so that if one goes out, the others do? Get a test light and start at the battery... work back to the tail end looking for bad wires... test the sockets... fuses? CHECK ALL BULBS... MAKE SURE THEY ARE ALL... ALL CORRECT! Electrical probs. Suck! Good luck..