Adherence of therapists to behaviors specified in cognitive-behavior therapy, interpersonal therapy, and clinical management manuals was studied. Raters used the Collaborative Study Psychotherapy Rating Scale (CSPRS) to rate therapist adherence in each of four sessions from 180 patients in the treatment phase of the National Institute of Mental Health Treatment of Depression Collaborative Research Program (TDCRP). Results indicate that therapists exhibited more behaviors appropriate to their own respective treatment approaches than to other treatment approaches. In fact, the three treatments could be discriminated almost perfectly using the CSPRS. Analysis of the psychometric properties of the CSPRS revealed high interrater reliability and high internal consistency. However, a five-component structure extracted from the intercorrelations of the CSPRS items was substantially different from a five-factor structure found in an earlier study.