16. Rabkin, S.W., Mathewson, F.A.L., Tate, R.B.: Predicting risk of ischemic heart disease and cerebrovascular disease from systolic and diastolic blood pressures. Ann Int Med 88: 342-345, 1978. The relative importance of systolic versus diastolic blood pressure in predicting risk of ischemic heart disease or cerebrovascular disease is controversial. Since 1948 we have observed in the Manitoba Study 3983 men (most between 25 to 34 years old at entry), in whom risk of both diseases was determined using the multiple logistic model. Systolic and diastolic blood pressures after adjustment for age and body weight were compared at entry and at four other examinations during the follow-up period. When both blood pressures were considered together, a stronger association with cerebrovascular disease was found for systolic compared to diastolic blood pressure at entry and at most of the other examinations. For ischemic heart disease, diastolic pressure showed a stronger association at the earlier examinations, whereas systolic pressure was more important when the majority of the cohort was between 40 to 50 years of age. In middle-aged men the general concept that diastolic is more important than systolic is not justified for cerebrovascular disease or for ischemic heart disease.