Arterial blood pressures (BPs) in 187 adult patients with sickle cell disease, casually recorded during hospitalization or clinic visits, were compared with BPs from age- and sex-matched populations of black Americans. The BPs in those with sickle cell disease were significantly lower than those in the control populations in all ages and did not demonstrate the expected rise with advancing age. In these patients, there was no difference between BP and sex, degree of anemia, or hemoglobin genotype. Four patients had diastolic and two had systolic hypertension. The prevalence of hypertension was significantly less than that in the block population. These BP findings in sickle cell disease may be due to the renal tubular defect responsible for increased sodium and water excretion, which may blunt the plasma volume expansion necessary for sustained hypertension and thus promote lower arterial pressures, similar to that situation observed in patients with salt-losing nephritis.