This study compares the effectiveness of Parent-Child Interaction Therapy (PCIT) in reducing behavior problems (e.g., aggression, defiance, anxiety) of 62 clinic-referred, 2- to 7-year-old, maltreated children exposed to interparental violence (IPV) with a group of similar children with no exposure to IPV (N=67). Preliminary analyses showed that IPV-exposed dyads were no more likely to terminate treatment prematurely than non IPV-exposed dyads. Results of repeated-measures MANCOVAs showed significant decreases in child behavior problems and caregivers' psychological distress from pre- to posttreatment for IPV-exposed and IPV nonexposed groups, and no significant variation by exposure to IPV. Stress in the parent role related to children's difficult behaviors and the parent-child relationship decreased from pre- to posttreatment, but parental distress did not decrease significantly over the course of PCIT. Results of an analysis testing the benefits of a full course of treatment over the first phase of treatment showed that dyads completing the full course of treatment reported significantly greater improvements in children's behavior problems than those receiving only the first phase of treatment.