This study assessed the utility of the Child Sexual Behavior Inventory (CSBI) in a child welfare sample. In this study, 97 children from ages 10 to 12 from either foster boarding homes or a residential treatment center participated. Researchers interviewed foster parents or primary therapists about children's sexual behavior, traumatic events, clinical symptoms, and their attitudes toward the child. Findings revealed that problematic sexualized behaviors were more prevalent in the residential treatment center (RTC) sample than they were in a normative sample. The pattern of associations between sexual behavior problems, traumatic events, and clinical syndromes in both the RTC and the foster boarding home (FBH) samples was similar to what has been found in samples in which biological custodial parents were the respondents. Analyses comparing youth who met the criterion for having problematic sexualized behaviors and youth who did not meet the criterion revealed that the two groups differed on clinical symptoms, prior traumatic events, and negative reports by caregivers. Results confirm the utility of the CSBI measure for this population and highlight several important clinical and programmatic concerns for addressing problematic sexual behavior in children in the child welfare system. (Contains 4 tables and 3 footnotes.)