It has been reported that radiation from GaAs electroluminescent diodes operated under forward bias conditions gradually decreases with time. This paper, which is a more comprehensive study of the effect, describes the results of a large-scale, systematic aging study (800 diodes, aged from 1600 to 8000 hr) for a wide range of fabrication parameters and stress conditions. The fabrication variables encompass junction formation, surface preparation, encapsulation, and crystal types. The stress conditions include current densities from 0 to 500 A/cm2 at room temperature and from 0 to 130 A/cm2 at 65°C. The effect of the above parameters on the rate of decay of the light output is presented. A marked decrease in the light decay rate is found for diodes which had the junction prepared by solution growth techniques. © 1967.