Physical and chemical characteristics of 8-hydroxyquinoline aluminum (Alq(3)) have been investigated in this work. The fluorescence stabilities of Alq(3) films were compared before and after UV irradiation. They were analyzed by using a UV-Vis absorption spectrophotometer, an in situ fluorescence spectrometer, attenuated X-ray photoelectron spectroscopy, and a nanosecond fluorescence spectrophotometer. Degradation in photoluminescence properties was significant in the presence of humid air (at an 85% relative humidity). These results indicate that water and oxygen aid the photodegradation, and the degradation mechanism of Alq(3) in the presence of H2O and O-2 is discussed in terms of chemical reactions.