Fourteen patients with sickle cell anemia, ages 6 to 20 years, were studied while ingesting high-and low-sodium diets. Although none of the patients had excessive urinary loss of sodium, the majority had elevated plasma renin activities and aldosterone secretion rates. The PRA was higher in patients over 10 years of age; ASR in patients receiving the high-sodium diet increased with age. Patients with sickle cell anemia appeared to compensate for urinary sodium loss between crises. The mechanism of this loss could be a defect in the function of either the distal tubule or the loop of Henle.