Physical responses to emotional tension of 97 patients were monitored by cardiovascular techniques while patients were in psychotherapy. Heart rates and blood pressures were measured, results of electrocardiograms analyzed, and voice transmission and videotapes studied. Evidence of arousal as measured by tachycardia, hypertension, and arrhythmias was more frequent than could be observed clinically. Depressed patients showed almost as much physical tension as those who were obviously angry or anxious. Variations that were difficult to see clinically were easily detected by monitoring.