The purpose of this study was to investigate the effectiveness and safety of enalapril in elderly people. A double-blind, randomized, placebo-controlled trial was carried out in 32 subjects aged from 75 to 97 years (mean: 86 years) with blood pressure values equal or superior to 160/90 mmHg. After 8 weeks of treatment with enalapril in doses of 20 to 40 mg/day, the systolic pressure was lowered from 190 +/- 16 to 151 +/- 19 mmHg (P less than 0.0001) and the diastolic pressure from 102 +/- 7 to 85 +/- 11 mmHg (P less than 0.0001). Systolic and diastolic pressures were also significantly reduced in subjects under placebo (from 183 +/- 16 to 165 +/- 21 mmHg, P less than 0.001; and from 101 +/- 9 to 91 +/- 13 mmHg, P less than 0.001, respectively), but the degree of reduction was significantly superior with enalapril (systolic: 39 +/- 25 vs 18 +/- 19 mmHg, P less than 0.005; diastolic: 17 +/- 13 vs 11 +/- 12, P less than 0.001); blood pressure was inferior to 160/90 mmHg in 67% of the subjects treated, as against 35% of those under placebo. Two patients under enalapril died: one on the 27th, the other on the 47th day of treatment. No relation could be established between these deaths and the drug, and this figure of 2 is not significantly different for the number of deaths expected over the same period in a population of that age-group. Among the patients under placebo, one had pulmonary embolism on the 34th day and another had a sudden increase in blood pressure on the 6th day, requiring discontinuation of treatment. It is concluded that enalapril administered alone is effective and well tolerated. Long-term studies are needed to find out whether this angiotensin-converting enzyme inhibitor is superior to a diuretic as initial treatment of arterial hypertension.