The purpose of this research is to characterize in adolescents blood pressure variations which might be indicative of future hypertension, utilizing a non-invasive portable method of blood pressure determination in ambulatory, free-living adolescents representative of the State of Maryland population and dichotomized by a documented family history of hypertension. The findings of these two groups will also be compared to those of adolescents with primary and secondary hypertension. This study will determine within-the-day fluctuations of blood pressure in adolescent members (12-18 years of age) of households chosen in a previous project as a probability sample of the Maryland population. The characteristics of the 24-hour blood pressure curves will be analyzed as the dependent variables in this descriptive epidemiologic study which will include variables of family data on hypertension, health and social status, and anthropometric, health, and life-style characteristics of the adolescents. Comparison will be made of the findings in respondents free of a family history of hypertension and those with a family history of hypertension. A group of adolescents with primary and secondary hypertension, ascertained through medical sources, will be similarly studied. The results of this study will provide a sound epidemiologic basis for future in-depth exploration of alterations of blood pressure characteristics which may be indicative of future hypertension.