Production of aldosterone and norepinephrine is examined in a mixed-longitudinal study design in white and Black boys and girls beginning at ages 6 to 12 and extending to age 17. Levels of these pressor systems are determined in the basal state from measurements made in urine samples collected overnight. To enhance the likelihood that school children would comply with the multiple observations required for this longitudinal study, measurements are deliberately restricted to non-invasive ones. Specifically, aldosterone and norepinephrine excretion measured in sleep urine are obtained at six month intervals in addition to blood pressure, heart rate, weight, height, and skin-fold thickness. Family history of hypertension and parental blood pressures are used as covariates in analysis of data in children. A second part of the study concerns the observation that blood pressure increases at a faster rate during adrenarche, a period of increasing adrenal androgen production, and during puberty. Androgen production during periods of adrenal and gonadal maturation may contribute to the increase in blood pressure. The relationship of androgen to blood pressure is examined by distinguishing blood pressure responses to androgen production from effects of androgens on physical growth, thus exploring the concept that androgens interact directly with pressor systems to raise blood pressure. Androgen production during the adrenarche is determined by measurement of dehydroepiandrosterone-sulfate excretion, and during puberty by measurement of luteinizing hormone excretion in sleep urine samples. Studies continue on the relationship between aldosterone excretion rate, dietary potassium intake, and blood pressure. A cross-over study is conducted to examine the effect of potassium supplementation on aldosterone production. Segregation analysis of the 'low-aldosterone'phenotype is performed on family members of children with low-aldosterone.