Data from the total urban elderly population (75 years and older) in Kungsholmen, Stockholm, were used to calculate age- and sex-specific prevalence of hypertension. Blood pressure was measured as part of the examination in the population survey (the Kungsholmen Project). The blood pressure of 1751 elderly people and any antihypertensive treatment were recorded. The prevalence of hypertension was 54 and 59 per 100 population for men and women, respectively. No great variation was observed with age or sex. Isolated systolic hypertension was most frequent with increasing prevalence in advanced ages, while isolated diastolic hypertension and systolic and diastolic hypertension showed a tendency of decreased prevalence with age. In the subjects studied, 18% were being treated for hypertension. Hypertension was detected in 47% of those not undergoing treatment. Among those, 76% had high blood pressure measurements. Our data demonstrate that hypertension is a prevalent disease in the very old, in both sexes, and support the need for hypertension screening programs as well as programs to evaluate the efficacy and benefits of treatment in this age group.