The aggregation of arterial blood pressure, weight, and height were compared between family members of children and adolescents with blood pressure percentiles at or above 95 (group 1) and at or below 50 (group 2). Weight, height, and systolic and diastolic blood pressures were significantly higher in siblings and target individuals of group 1 (p less than 0.001). Weight and systolic and diastolic blood pressures were significantly higher in mothers of group 1 (p less than 0.001). Covariant analysis comparing the average systolic and diastolic blood pressures of both groups controlled by age, age and weight, and age and Quetelet index revealed that the arterial blood pressure of mothers, siblings, and target individuals remained higher in group 1 (p less than 0.05 to p less than 0.001). These observations show a strong familial aggregation of arterial blood pressure not dependent only on physical development and also raise the question of a genetic basis as a possible mechanism of systemic arterial hypertension.