Anatomical and functional renal medullary abnormalities are common in patients with sickle cell disease (HbSS) and sickle cell trait (HbAS). Sickle cell disease is associated with impaired urinary potassium excretion, but renal potassium handling in patients with HbAS has not been reported. To address this question, we gave nine HbAS and eight black control (HbAA) volunteers an oral potassium chloride load (0.75 mEq/kg of body weight), collected urine for five hours, and measured changes in the serum and urinay potassium levels. Both prior to and after potassium chloride loading, there were no differences between groups in serum or urinary potassium levels nor in percent of excretion of administered potassium. We conclude that patients with HbAS, despite decreased concentrating ability, have no impairment of the renal response to oral potassium loading and no apparent increased risk of hyperkalemia during periods of high potassium intake.