OBJECTIVES The goal of this study was to evaluate the role of diastolic blood pressure (DEP) in cardiovascular mortality for different systolic blood pressure (SBP) levels in middle-aged men and women. BACKGROUND In middle-aged subjects it is unclear whether DEP, in addition to SEP, should be considered for risk evaluation. METHODS Subjects (77,023 men; 48,480 women) aged 40 to 70 years old, had no major cardiovascular disease, no antihypertensive treatment and were examined at the Centre d'Investigations Preventives et Cliniques between 1972 and 1988. Mortality was assessed for an 8- to 12-year period. RESULTS In both genders, cardiovascular mortality increased with the SEP level. In men and women with normal SEP levels, DEP did not influence cardiovascular mortality after adjustment for age and SEP. In men with systolic hypertension, a U-shaped curve relationship between cardiovascular mortality and DEP was observed, with the lowest mortality rates in the group with DEP 90 to 99 mm Hg. Compared with this group, age- and SEP-adjusted cardiovascular mortality was higher by 73% (p < 0.02) in the group with DBP <90 mm Hg and by 65% (p < 0.001) in the group with DBP <greater than or equal to>110 mm Hg. In women with systolic hypertension, however, DBP was positively correlated with cardiovascular mortality. CONCLUSIONS In middle-aged subjects, classification of cardiovascular risk according to DEP revels should take into account gender, especially when SEP levels are elevated. Men with systolic hypertension are at higher risk when their DEP is "normal" than when they present a mild to moderate increase in DBP. In women of the same age, however, systolic-diastolic hypertension represents a higher risk than isolated systolic hypertension. a Am Cell Cardiol 2001;37:163- 8) (C) 2001 by the American College of Cardiology.