Patterns of pulse rate, blood pressure (BP), and body size and composition are investigated in a black urban sample of over 600 adolescents (aged 12-17) in Philadelphia as part of the Philadelphia Blood Pressure Project. Supine and seated pulse rates decline after the age of 13 in both males and females, and females have significantly higher pulse rates than males, ranging from 1.6 to 4.7 beats/30 sec higher depending upon chronological age and position. Seated pulse rates are consistently higher than supine in both sexes ranging from 1.3 to 2.9 beats/30 sec depending upon chronological age. Pulse rate and both systolic blood pressure (SBP) and diastolic phase IV blood pressure (DBP) show a positive association throughout adolescence for females (r = 0.16 SBP, r = 0.24 DBP) but not for males (r = -0.06 SBP, r = 0.06 DBP). Females in the highest diastolic IV blood pressure stratum (greater than 85%) maintain higher pulse rates throughout adolescence, while males with the highest DBP have higher pulse rates in early adolescence (ages 12-14) but lower pulse rates in later adolescence (ages 16 and 17). Females with the highest DBP also show consistently higher measures of relative fatness (triceps skinfolds) throughout adolescence. Males with the highest DBP have greater triceps skinfolds in early adolescence and lower triceps in later adolescence, a pattern similar to that shown for pulse rate. For DBP, triceps is significantly and positively associated with pulse rate in the upper DBP percentile group (p less than 0.05). Thus, females with the highest blood pressure during adolescence are characterized by higher pulse rate and greater fatness. Males show this same pattern in early adolescence; whereas, in contrast, the older adolescent males in our sample with the highest DBP are characterized by lower pulse rates, relatively decreased fatness, and increased muscularity. Our findings suggest that, at least in some older black male adolescents, a higher DBP may reflect a decrease in cardiac output as indicated by a lower pulse rate, or an increase in peripheral vascular resistance, possibly associated with relatively decreased fatness and increased muscle mass for size.