ObjectiveTo determine the risk of death from coronary heart disease, stroke, all cardiovascular disease and all-cause mortality associated with systolic blood pressure and in particular with isolated systolic hypertension among the middle-aged population.Methods and designA prospective 15-year cohort study of two independent cross-sectional random samples of subjects participating in baseline surveys in 1972 and 1977. Each survey included a self-administered questionnaire, measurements of height, weight and blood pressure and the determination of the serum cholesterol concentration.SettingNorth Karelia and Kuopio provinces in eastern Finland. Mortality follow-up complete with the personal identification number.ParticipantsParticipants were 10 333 men and 11 160 women aged 25–64 years without histories of myocardial infarction and stroke incidence at the time of the baseline survey. Isolated systolic hypertension in these analyses was defined as systolic blood pressure ≥ 160 mmHg and diastolic blood pressure < 95 mmHg. Subjects with blood pressure < 160/90 mmHg were considered normotensive.ResultsCoronary heart disease, stroke, cardiovascular disease and all-cause mortality among men and women aged 45–64 years increased with the increasing systolic blood pressure. Among women aged 45–64 years, isolated systolic hypertension increased the relative risk of these fatal events. Among men aged 45–64 years, only coronary heart disease mortality was significantly associated with isolated systolic hypertension.ConclusionIsolated systolic hypertension is an important predictor of death from coronary heart disease, stroke, cardiovascular disease and all causes for women. For men aged 45–64 years, the risk of death from coronary heart disease was associated with isolated systolic hypertension, but the risk of stroke, cardiovascular disease and all-cause mortality associated with increasing systolic blood pressure was evident already at the systolic blood pressure levels < 160 mmHg, independently of the level of diastolic blood pressure.J Hypertens16:577–583 © 1998 Lippincott-Raven Publishers.