To study the relation of habitual physical activity, diet, and serum lipoproteins to blood pressure, a cross-sectional study was carried out in a cohort of 202 women, age 60-69 yr. Sitting, supine, and standing blood pressure was measured with a standard sphygmomanometer. Physical activity was assessed by questionnaire, diet by food records, serum lipoprotein cholesterol enzymatically, and apolipoprotein AI turbidimetrically. Among the women not taking antihypertensive medication (N = 127), the physically most active (physical activity 5 times per week or more) had sitting diastolic blood pressure of 86 mm Hg (adjusted for high-density-lipoprotein cholesterol, body mass index, and cardiovascular health status), which was 8 mm Hg lower (P = 0.007) than in the least active (physical activity twice per week or less) women. Subjects in the highest tertile of apolipoprotein AI (> 1.46 g.l-1) had a mean sitting systolic blood pressure of 147 mm Hg (adjusted for age, body mass index, and cardiovascular health status), which was 16 and 13 mm Hg lower (P = 0.001) than in women in the middle and lowest tertiles (< 1.32 g.l-1), respectively. The present data suggest that, in elderly women, regular physical activity is associated with a clinically significant lowering of diastolic blood pressure. Moreover, a higher level of serum apolipoprotein AI, the major protein component of high-density lipoprotein particles, is inversely associated with systolic blood pressure.