This paper aims to clarify the effect of oxygen on dislocation multiplication in silicon single crystals grown by the Czochralski and floating zone methods using numerical analysis. The analysis is based on the Alexander-Haasen-Sumino model and involves oxygen diffusion from the bulk to the dislocation cores during the annealing process in a furnace. The results show that after the annealing process, the dislocation density in silicon single crystals decreases as a function of oxygen concentration. This decrease can be explained by considering the unlocking stress caused by interstitial oxygen atoms. When the oxygen concentration is 7.5 x 10(17) cm(-3), the total stress is about 2 MPa and the unlocking stress is less than 1 MPa. As the oxygen concentration increases, the unlocking stress also increases; however, the dislocation velocity decreases. (C) 2018 Elsevier B.V. All rights reserved.