A method and a device for controlling a brake system of a motor vehicle having an electrical drive unit and two brake circuits is described in DE 196 04 134 A1. When the vehicle is decelerated using the electrical drive unit for simultaneously charging a battery, the hydraulic braking torque applied to at least one wheel by the wheel brake cylinders of the two brake circuits should be reduced/deactivated in spite of manipulation of the brake pedal. To that end, the pressure medium displaced from the master brake cylinder to the wheel brake cylinders via manipulation of the brake pedal should be counteracted, in that the pressure medium displaced from the master brake cylinder is transferred into the accumulators of the two brake circuits by opening the exhaust valves of the two brake circuits. In this manner, regenerative braking carried out by the electrical drive unit should be able to be blended. If the exhaust valves used may only be activated for a short time due to thermal reasons, the two exhaust valves of a brake circuit should be activated in an alternating manner.