In a population-based study, three groups of individuals were examined: 334 hypertensive subjects (group 1) received 7 years of intervention therapy by a Hypertension Team (HyT); 418 subjects (group 2) were simply observed with blood pressure (BP) measurement on demand and given lifestyle advice; and 437 subjects (group 3) had no contact with HyT. Hypertension intervention therapy was then withdrawn, leaving patients to their general practitioners. After phase A, BP was significantly lower than baseline in group 1 (-14.2%, P < .01) and group 2 (-12.4%, P < .01), whereas it was unchanged in group 3. Cerebrovascular (but not coronary) events were observed less in group 1 (fatal 2.7%, nonfatal 3.7%) than in group 2 (7.2% and 5.2%, respectively, both P < .001 v group 1) or group 3 (8.3% and 6.9%, respectively, both P < .001 v group 1). During a further 7 years of observation (phase B), no between-group differences in mortality were observed. We conclude that simple observation improves BP control, but that intervention is needed to reduce the incidence of stroke.