This study explores the relationship of chronic stress to hypertension. The study included 127 hospitalized and 134 outpatients of a stress treatment program and 129 "normal" persons in the general population. All subjects were matched for age, sex, and race. After three days of hospitalization, there was a 17.3% incidence of hypertension in the hospitalized patients when hypertension was defined as blood pressure levels greater than 140/90 mmHg. These data compare with a 5% and 13% incidence of hypertension in the outpatient stress and "normal" groups, respectively. The National Health Survey of 1962 indicated that 18% of the population were hypertensive. Our data indicate that the incidence of hypertension was no greater in a diagnostically established group of hospitalized stress patients than in the less stressed outpatient or an otherwise "normal" group. The frequently expressed notion that tension and chronic stress predispose a population to essential hypertension is not confirmed by this analysis.