The efficacy and the mechanisms of action of two behavioral treatments for essential hypertension were compared: cognitive group therapy for anger control and biofeedback for heart rate control. The cognitive therapy aimed at lowering the "general anger" level and helping overt expression of "anger out;" heart rate biofeedback aimed at slowing heart rate in stress situations. Ninety-seven essential hypertensive patients were randomly assigned to three groups; after 20 dropouts, 77 patients fully participated in the study: cognitive treatment (N = 30), biofeedback (N = 27), and control (no treatment, N = 20). The treatments were held in 17 weekly sessions; during treatment, blood pressure was measured once a month, and during follow-up after 1 and 6 months. The anger level and heart rate control were assessed at the beginning and the end of treatment. The main results were: 1) a significant decrease of blood pressure for both treatments as compared with control, 2) a significant decrease of blood pressure with heart rate biofeedback as compared with cognitive therapy, and 3) a better control in anger achieved with cognitive therapy and a lesser control in heart rate as compared with biofeedback.