A randomised trial of the treatment of hypertension in 884 patients aged 60 to 79 years at the onset showed a reduction of 18/11 mm Hg in blood pressure over a mean follow up period of 4.4 years. The principal antihypertensive agents were atenolol and bendrofluazide. There was a reduction in the rate of fatal stroke in the treatment group to 30% of that in the control group (95% confidence interval 11-84%, p less than 0.025). The rate of all strokes (fatal and non-fatal) in the treatment group was 58% of that in the control group (95% confidence interval 35-96%, p less than 0.03). The incidence of myocardial infarction and total mortality was unaffected by treatment. Questionnaires completed by the patients and their relatives failed to identify any differences in symptoms that were likely to be due to treatment.