The European Working Party on High blood pressure in the Elderly (EWPHE) trial was a double-blind randomized placebo-controlled trial of antihypertensive treatment in patients over the age of 60 years. Entry criteria included both a sitting diastolic blood pressure on placebo treatment in the range of 90-119 mmHg and a systolic blood pressure in the range of 160-239 mmHg. Eight-hundred and forty patients were randomly assigned either to active treatment (hydrochlorothiazide + triamterene) or a matching placebo. If blood pressure remained elevated methyldopa was added to the active regimen and matching placebo to the placebo regimen. Before randomization, the patients were stratified in eight strata according to sex, age groups between 60 and 69 years or 70 years and over, and the presence or absence of cardiovascular complications of hypertension. Both the intention-to-treat and 'on randomized treatment' analyses suggested a benefit from active treatment in men and women. Formal statistical significance was achieved for male cardiovascular mortality (intention-to-treat analyses) and for cardiovascular events in females. Although the event rates were greater for patients with previous cardiovascular events and patients over the age of 70 years, the percentage reduction in cardiovascular events was similar in these groups to those without complications and in patients between 60 and 69 years of age. However, little benefit from treatment could be demonstrated in patients over the age of 80 years. The presence or absence of smoking had no influence on response to treatment in these elderly patients.