Male patients, born between 1900 and 1925, have been entered in a study to ascertain the effect of therapy on the lifespan of people with different levels of blood pressure. Patients were divided into three groups--those with diastolic blood pressure below 12.6 kPa (95 mmHg), those with diastolic blood pressure between 12.6 kPa and 14.5 kPa (95 mmHg and 109 mmHg), and those with diastolic blood pressure higher than 14.6 kPa (110 mmHg). Patients in the first group were not treated, and all patients in the last group were treated. Patients in the middle group were subdivided into four subgroups, one of which received no treatment. Those in the second subgroup were placed on a reduced salt intake diet; those in the third subgroup were given a thiazide diuretic followed by alpha-methyldopa; and patients in the fourth subgroup were given a beta-blocking drug followed by a thiazide diuretic. The mortality rates in all groups, except one, were similar, and similar to that predicted for a normal population. The patients who were treated with thiazide diuretic regimen had a higher mortality rate which was due to a greater number of fatal myocardial infarcts and sudden deaths. These occurred in the first 2 1/2 years of therapy, and the cause of this is unknown. In this study, therapy did not produce an improvement in the lifespan of elderly males with hypertension.