We investigated the influence of carbon addition on oxygen solubilities in silicon melts. Oxygen concentration increases with increasing carbon concentration in silicon melts when melt temperatures are above 1470 degrees C. The temperature dependence of oxygen concentration in carbon-doped silicon melts is strong when carbon concentration is above 5.0 x 10(17) atoms/cm(3). It is found that 87% of the oxygen atoms are related to carbon in carbon-doped silicon melts when carbon concentration is 3.0 x 10(18) atoms/cm(3) and silicon melt temperature is 1500 degrees C.