Blood pressure and body mass index (BMI) are first considered independently, and then jointly, on the basis of both cross-sectional and longitudinal epidemiologic studies. The relations between these two attributes are investigated further by analysis of the "velocity curves" of age increments, from ages 6 to 24, in both blood pressure (systolic and fifth-phase diastolic) and BMI, from data from the US Health and Nutrition Examination Survey, 1971-1974. The results of both reported studies and the present exploratory analysis indicate sometimes strong but quite variable relations between blood pressure and BMI, which differ by age, gender, and the particular blood pressure measure under consideration.