We investigate minority-carrier trapping centers in p-type Czochralski (Cz) silicon by means of the quasi-steady-state photoconductance method. Boron and gallium-doped Cz silicon wafers of varying resistivities and oxygen contamination levels are examined. A clear correlation of the trap density with the interstitial oxygen concentration as well as with the boron and the gallium concentration is detected. The experimental data suggest that oxygen is a direct component of the defect complex responsible for the trapping, while the role of boron and gallium is not fully resolved. Using a simple single-level trapping model, we determine the energy level and the trapping/detrapping time constant ratio of the oxygen-related trapping center.