The longitudinal comparison of the cardiovascular responses of adolescent twins and their parents was initialed in 1983. Three cohorts of twin families were enrolled, each cohort beginning 18 months apart. Both monozygotic and dizygotic twins were included. Variables measured included demographics, family history, personality, blood pressure, anthropometry, stage of puberty, dynamic exercise, isometric exercise, psychological stress, echocardiography, genotyping, and lipid profiles. Each cohort revisited every 18 months.