This paper presents experimental results of the onset of SiO2 growth at high temperatures ranging from 800 to 1000°C, and reviews observations made on the intitial stages of silicon oxidation at low temperatures ranging from 300 to 700°C, and native-oxide growth at room temperature. An incubation period of duration TD, during which the oxide does not grow at the onset of oxidation at all temperatures, is observed. The dependence of the delay TD on substrate orientation, doping, and oxidation temperature is summarized. A model exploring the influence of SiO formation at the onset of the thermal oxidation of silicon at high temperatures in dry oxygen on the passive-to-active oxidation transition is presented. © 1995.