To determine if hypertensives and normotensives of similar ages had, on average, different ratios of 24-hour to overnight excretion of sodium, potassium, and water. Also, to determine the number of 24-hour collections needed to characterize individuals with respect to the ratios of 24-hour to overnight excretion and to determine if the ratios of 24-hour to overnight excretion vary by age and other factors related to blood pressure.