I WAS APPROACHING A RED LIGHT AT LOW SPEED (20-15MPH) ON A RAINY MORNING ON CITY STREETS. I DEPRESSED THE BRAKE PEDAL AND IT WENT ALL THE WAY TO THE FLOOR WITHOUT STOPPING THE CAR EFFECTIVELY (THE CAR SLOWED BUT DID NOT STOP AS IT NORMALLY WOULD HAVE IF THE BRAKES WERE FUNCTIONING NORMALLY). AS A RESULT, I ENTERED THE INTERSECTION AND HIT (AT LOW SPEED) ANOTHER AUTOMOBILE THAT HAD THE GREEN LIGHT. THERE WAS MODERATE DAMAGE TO BOTH VEHICLES BUT NO PERSONAL INJURIES.