The current study evaluated the factor structure of the forms and functions of aggression measure developed by Little, Jones, Henrich, and Hawley (2003) in a clinical inpatient sample using child and caregiver reports. Confirmatory factor analyses were conducted with a sample of 189 children ranging in age from 6-12 years residing in a child psychiatric inpatient facility. The factor structure was replicated in this sample for both child and caregiver reports of aggression. Child and caregiver reports of proactive, but not reactive, aggression were associated with conduct problems. The implications of our findings are discussed for both research and practice. Copyright © Taylor & Francis Group, LLC.