Pain catastrophizing is an important cognitive construct that has been linked with many aspects of the pain experience, including pain intensity, emotional distress, pain-related disability, and pain behavior. The Pain Catastrophizing Scale (PCS), an instrument often used to assess this construct, reflects three aspects of catastrophizing: Rumination, Magnification, and Helplessness. Its factor structure, however, has never been examined in clinical samples of persons with occupational injury or as a function of race. In this study, exploratory and confirmatory factor analyses were used to examine the factor structure of the PCS in a large, racially diverse sample of Workers' Compensation claimants with low back injuries. Results indicated that a two-factor model of the PCS (Rumination and 'Powerlessness,' the latter a combination of the PCS Magnification and Helplessness scores) was the most parsimonious fit to the data, particularly in the African American sample. Future research in other clinical samples that include African Americans is needed to examine the stability of the results reported here.