A straightforward dc circuit has been built for the precise regulation and accurate measurement of the total incident beam current in an elastic low‐energy electron diffraction (ELEED) apparatus. It functions simply by comparing the returning ground current to a reference current and optically coupling the result to control the filament‐to‐Wehnelt cylinder potential difference. Beam currents down to 0.1 &mgr;A are regulated to within 1% at sweep rates up to 8 v/sec and energy ranges up to 200 eV wide. An additional useful feature is the ability to monitor and null out any leakage or displacement currents without confusion with the true beam current.