One hundred and one patients, 70 experimental and 31 controls, with a diagnosis of essential hypertension, were examined for the effects of group relaxation training and thermal biofeedback on blood pressure and on other psychophysiologic measures: heart rate, forehead muscle tension, finger temperature, depression, anxiety, plasma aldosterone, plasma renin activity, and plasma and urinary cortisol. Eighty percent of the participants were medicated. Treatment yielded a short-term success rate, defined as a decrease in mean arterial pressure of 5 mm Hg, of 49% in the experimental group. Other significant short-term changes included a reduction of forehead muscle tension, state anxiety, plasma aldosterone, and increased finger temperature. Follow-up measurements were made approximately 10 months after treatment in 36 patients, 51% of the treatment completers. Twenty of the 36 were short-term treatment failures, while 16 were treatment succeeders. Thirty-seven percent of the short-term succeeders continued to meet blood pressure criterion at follow-up. In short-term succeeders, continued practice of relaxation may influence long-term maintenance of decreased blood pressure. It is suggested that group relaxation training can be beneficial for short-term and long-term adjunctive treatment of essential hypertension in selected individuals.