Compared to the Czochralski (CZ) silicon used in microelectronic industry (M-CZ Si), the annealing behavior of oxygen in the CZ silicon used for solar cells (S-CZ Si) was investigated by means of FTIR and SEM. It was found that the oxygen concentration in S-CZ Si crystal was lower than in the M-CZ Si crystal. During single-step annealing in the temperature range of 800-1100degreesC, the oxygen in S-CZ Si was hard to precipitate, even if the material contained higher carbon concentrations. After pre-annealing at 750degreesC, many more oxygen precipitates were formed, The amount and density of the oxygen precipitates were almost the same as in M-CZ Si annealed in single step. It is considered that oxygen has no significant influence on the efficiency of solar cells made from Cz silicon if it is annealed only by a single step in the range of 800-1100degreesC. (C) 2002 Elsevier Science B.V. All rights reserved.