Czochralski growth of silicon crystals is always related to transport Of impurities. The main impurities are oxygen and carbon. They react with furnace elements with formation of SiO, SiO2 and SiC deposit layer, Prediction of transport of impurities is important to detect the precise location of areas where impurity deposition may cause considerable difficulties and to avoid excessive deposition above the melt free surface. Detailed analysis of chemical processes, accompanying Cz silicon growth is under discussion in the Current paper. The proposed numerical model accounts for oxygen transport in the melt and SiO deposition on the walls of the furnace. Computer analysis was provided for cases with different heat insulation of the furnace walls. (C) 2008 Elsevier B.V. All rights reserved.