The current study undertook a narrative and meta-analytic review of the literature to examine the effectiveness of group-based in-service foster parent training programs in reducing externalizing child behaviors. All studies reported a significant decrease in at least one measure of child behavior problems for treatment-group participants. The programs appear to be effective across ethnically and nationally diverse samples and produce similar results for older and younger children, as well as boys and girls. Overall the evidence suggests that group-based foster parent programs are an effective method for reducing problem behaviors among children in out of home care.