There is a general belief that the oxidation of silicon is due to the transport of molecular oxygen through the growing oxide. However, several recent experimental results have shown that atomic oxygen is also a possible candidate fur the transported species. This paper discusses which of these two candidates is the most likely transported species, considering both traditional arguments and these based on more recent experimental results. This discussion shows that the experimental results traditionally used as arguments for molecular oxygen being the transported species are equally valid for atomic oxygen as the transported species. However more recent experimental results strongly support atomic oxygen, not molecular oxygen, as the transported species. The conclusion is that atomic oxygen is the more likely candidate For the transported species in the oxidation of silicon.