The more recent works dealing with the study of oxygen self-diffusion in ZnO have shown that the oxygen diffusion takes place by means of doubly negatively ionized interstitial oxygen. This oxygen diffusion mechanism in zinc oxide is reviewed and based on experimental data of oxygen self-diffusion and electrical conductivity; for Al-doped and undoped ZnO, it is suggested that oxygen self-diffusion in ZnO takes place by means of an interstitial mechanism, but with the interstitial oxygen having a null or a single negative effective charge. (C) 2003 Elsevier B.V. All rights reserved.