The reliability of AlGaInP double‐heterostructure (DH) light‐emitting diodes (LEDs) operating typically at 600 nm has been studied. To investigate degradation, accelerated aging at ambient temperatures of 50, 75 and 125°C has been carried out for over 5000 h. The activation energy of homogeneous degradation was determined to be 0.8 eV and an extrapolated half‐life in excess of 106 h was estimated at an ambient temperature of 20°C. Copyright © 2000 John Wiley & Sons, Ltd.