Among the first screened 2439 males born in 1926 and 1927, aged 48-49 years at the time of screening and representing 76% of these age cohorts, uncontrolled or partly controlled hypertension was found in 7.5%. Of these individuals, 30% preferred to remain with their physicians, regardless of the degree of control they had achieved. Among those who were referred to the Hypertension Unit (5.2% of the screened population), elevated S-GT levels (greater than or equal to 1.10 mukat/l) were found in 38.3%, against 18.5% in the two cohorts. During 24 months of treatment and follow-up only two men among the entire group of hypertensives referred dropped out, both were heavy drinkers (greater than 80 g alcohol daily). The mean BP after treatment was significantly lower among men with normal than high S-GT values or in those who admitted to heavy drinking. Of the 99 males treated for more than two years, 82 (83%) were responders (supine DBP less than or equal to 95 mmHg). Of the non-responders, 70% were either heavy drinkers or had abnormal S-GT values. The possible role of alcohol in the pathogenesis of essential hypertension in middle-aged males is discussed.