Photoluminescence (PL) was used as an in situ method for studying the electrodeposition of copper on p-GaAs. During electrodeposition, PL of GaAs decayed due to growth of the metallic layer and the PL signal was sensitive to a fraction of a monolayer of copper. Recovery of the initial PL intensity was observed after anodic stripping of the copper deposit. A quantitative empirical relationship was established between the PL decrease and the amount of deposited copper, Variation in PL intensity is mainly due to modification of the optical properties of the interface rather than to a change in semiconductor band bending. PL can be a convenient method for monitoring metal electrodeposition on other semiconductors too.