The interface formed between tris(8-hydroxyquinoline) aluminum (Alq(3)) and electrodes (Al and ITO) of light emitting diodes was examined by X-ray photoelectron spectroscopy (XPS). Upon deposition of aluminum layer, Alq(3) reacts partially with the metal, forming metallic carbide and/or Al-O-C complex in the interfacial region. On the Alq(3)/ITO side, no noticeable change in the spectra was observed. Analysis of the organic material/electrode interface was also performed on the devices after several working cycles up to their complete destruction. Compared to non-degraded samples, the interface between Alq(3) and Al of degraded samples was modified by the diffusion of indium from the ITO base electrode to the upper Alq(3)/Al interface and aluminum from the upper electrode to the Alq(3) layer. In the ITO/Alq(3) interface, partial decomposition of the oxide layer occurred, leaving indium to diffuse throughout the emitting layer. The structural changes of the contact region is proposed to be one of the possible causes of the diode failure.