This study examined psychotherapy process in the National Institute of Mental Health Treatment of Depression Collaborative Research Program. Transcripts of brief interpersonal and cognitive-behavioral therapies were rated using the Psychotherapy Process Q Set (PQS), an instrument designed to provide a standard language for describing therapy process. Results demonstrated that there were important areas of overlap and key differences in the process of the treatments. There were important differences in therapist stance, activity, and technique that were consistent with theoretical prescription, but patient characteristics within sessions were quite similar. Patient in-session characteristics as measured by the PQS were related to outcome across the treatment samples. These findings are linked to theoretical models, which may help explain the role of nonspecific factors associated with nondifferential treatment outcome in brief therapy.