Discuss crhenry's answer to: Our 1995 toyota brake lights are stuck on. We have a bad master cylinder,would this causeit?

The brake light switch is activated by brake fluid pressure when the brakes are applied.  If the master cylinder does not completely release the pressure when you remove you foot from the brake pedal, the pressure will keep the brake lights on.  When you correct the master cylinder the problem will be solved also.  The brake light switch could also be bad, but I would wait until the master cylinder is repaired.