Abstract: Apparatus is provided for achieving and maintaining gray scale tracking in a multibeam, cathode ray display device, despite fluctuations in the electrical characteristics of the display device and of video amplifiers driving the device. Tracking is accomplished by measuring the actual beam currents produced during the applications of test signals to the amplifiers and automatically adjusting the biases and gains of the amplifiers in response to differences between the measured beam currents and predefined beam currents which should be produced. The invention can also be used to automatically stabilize the beam current in a single beam cathode ray display device.