In psychotherapy, effectiveness of an experimental treatment often is compared to care as usual. However, little if any attention has been paid to the heterogeneity of care as usual. The authors examined the effectiveness of manualized behavior therapy on school-aged disruptive behavior disordered (DBD) children in everyday clinical practice. A total of 77 DBD children (8-13 years) were randomly assigned to the Utrecht Coping Power Program (UCPP) condition or the care as usual condition. Care as usual consisted of family therapy (FT) or behavior therapy (BT). Decrease in parent-reported overt aggression was significantly larger in the UCPP condition than in the FT condition, but UCPP and BT did not differ significantly in this respect. The effect sizes of difference scores on other variables were more in favor of UCPP when compared to FT than to BT. The comparison of an experimental treatment to care as usual depends on the type of usual treatment. (Contains 3 tables.)