A brightness compensation system and method of providing brightness uniformity in an active-matrix organic light-emitting diode (OLED) flat-panel display. The brightness compensation system of the present invention includes a system controller, a timing generator, a test brightness generator, a pixel address generator, a video formatter, a first and second multiplexer, a memory device, a pixel adjust device, a level shifter and driver, a current sensor, an analog-to-digital converter, a DC power supply, and an active-matrix OLED display under test. The brightness compensation system and method of the present invention subjects an active-matrix OLED display to a testing operation that alternately tests every pixel, detects its output current, which is an indicator of light output level, for a given input voltage, saves the output current value in memory, then applies a corrective voltage to each pixel, so that each pixel has the same light output (output current) as its neighboring pixel.