This study was conducted to evaluate aggression and noncompliance among child psychiatric inpatients in relation to demographic, clinical, and hospitalization characteristics, including the use of restraints and seclusion. Eighty six children (10.8+/-2.4 years old, 67% male) consecutively admitted to an inpatient psychiatric unit were rated weekly using the Modified Overt Aggression Scale (MOAS) and the Disruptive Behavior Rating Scale (DBRS) between November 1, 2002 and June 30, 2003. Moderate to high correlations were observed between the four types of aggression (verbal, and physical against self, others, or objects) and noncompliant behavior. In hierarchical regression analyses, only mental retardation emerged as a significant predictor of aggression and noncompliance. Aggression and noncompliance were associated with different characteristics of inpatient treatment. Aggressive behavior was significantly associated with the use of restraints and seclusion, and noncompliant behavior with length of hospitalization and number of psychiatric medications at time of discharge. Modifying milieu interventions for youths with mental retardation, and adapting behavioral interventions empirically proven to target noncompliance may be effective loci for reducing aggression in child psychiatric inpatient units.