The out-diffusion profiles of oxygen from Czochralski grown (Cz) silicon were measured with secondary ion mass spectrometry for several processing conditions. The diffusivity of oxygen was found to be retarded under oxidizing conditions. This effect, however, is eliminated with the addition of 2% HCl to the oxidizing ambient. Both in-diffusing boron and in-diffusing phosphorus enhance the diffusivity of oxygen. These observations are consistent with a vacancy dominant diffusion mechanism for oxygen in silicon. The surface concentration of oxygen Cs varies considerably with processing conditions. An increased concentration of oxygen at the surface was observed under oxidizing conditions. Under inert or reducing conditions, Cs was lower than oxidizing conditions but did not approach as low a value as was expected. The lowest values of Cs were obtained for the phosphorus diffusion, boron diffusion, and for the 10% HCl oxidation.