This article describes studies on oxidative-photodegradation of cured Epolite epoxy resin using techniques of IR spectroscopy with attenuated total reflectance optics and scanning electron microscopy. The results show that the oxidative-photodegradation of this epoxy system is characterized by the formation and subsequent decomposition of carbonyl groups and by epoxy ring opening. The carbonyl bonds are apparently formed in the initial stage of photodegradation and then decomposed upon further aging. Changes in the surface morphology of the samples during degradation suggest that there is significant scissioning of the cross-linked polymer structure. This phenomenon was reproduced using three different UV lamps that differed in spectral properties. Our studies provide clues to the mechanism of epoxy polymer degradation by solar light. © 1994 John Wiley & Sons, Inc.