An experiment was carried out to study oxidation‐enhanced and oxidation‐retarded diffusion (OED and ORD) of Sb in (100) and (111) Si wafers oxidized in dry O2at 1160 °C. The ORD data of (100) wafers agree well with those of Mizuo and Higuchi and with the prediction of a model assuming that Si self‐interstitials and vacancies coexist in Si in thermal equilibrium at high temperatures. A small adjustment to the interstitial supersaturation values is needed to bring the ORD/OED data of (111) wafers to fit with the model satisfactorily. This indicates the existence of a mechanism which injects vacancies into (111) wafers in addition to the normal mechanism of interstitial injection due to SiO2growth.