1988 Oldsmobile cutlass supreme brake lights wont turn off?

you may want to make sure you have a DUAL(meaning TWO pieces of wire inside the bulb) filament bulb on the brake lights, if you just replaced the bulb and used a MONO filament bulb it will cause this to happen. If this isn't the case, you may want to take it to a mechanic to make sure the sensor that senses when you are pushing the pedal isn't stuck or out that would also cause the same problem.