A computer model for the fluid flow and dopant transfer/segregation in Czochralski crystal growth (CZ) and in Czochralski crystal growth in an axial magnetic field (MCZ) is applied to the simulation of the oxygen source, transport, and segregation in CZ and MCZ silicon growth. To model the oxygen source, which is ablation of the silica crucible, the oxygen concentration at the melt/crucible interface is assumed to be at an equilibrium concentration which is dependent on temperature as described by Arrhenius kinetics. The oxygen sink is mostly evaporation of silicon monoxide from the melt-free surface; a small percentage of the dissolved oxygen is incorporated into the growing crystal. Good agreement is established between the simulated oxygen radial profiles and experimental results in CZ/MCZ silicon growth, as well as in the comparison of the simulated ablation rate of the crucible with the experimental data reported to date. © 1991, The Electrochemical Society, Inc. All rights reserved.