We report an optical degradation of an InGaN/AlGaN double‐heterostructure light‐emitting diode (LED) on a sapphire substrate grown by metalorgonic chemical vapor deposition. Electroluminescence, electron‐beam induced current, and cathodoluminescence observations have shown that the degraded InGaN/AlGaN LED exhibits formation and propagation of dark spots and a crescent‐shaped dark patch, which act as nonradiative recombination centers. The values of degradation rate under injected current density of 0.1 kA/cm2 were determined to be 1.1×10−3, 1.9×10−3, and 3.9×10−3h−1 at ambient temperatures of 30, 50, and 80°C, respectively. The activation energy of degradation was also determined to be 0.23 eV. © 1996 American Institute of Physics.