One hundred seventeen patients with anemia related to chronic renal failure not severe enough to require maintenance dialysis were randomly assigned to receive recombinant human erythropoietin (rHuEPO; 50,100, or 150 U/kg body weight) or placebo intravenously (IV) three times a week for 8 weeks or until their anemia was corrected. Correction of anemia (hematocrit of 40% for males, 35% for females) occurred in 87% of those given 150 U/kg, 64% of those given 100 U/kg, 46% of those given 50 U/kg rHuEPO and in 3% of the placebo group. Energy levels and work capacity improved significantly in the group with corrected anemia compared with the group with uncorrected anemia. rHuEPO appeared to be well tolerated. There was no evidence that rHuEPO therapy accelerated the deterioration of renal function as measured by serum creatinine and reciprocal of serum creatinine compared with placebo treatment. However, it is essential that blood pressure and hematocrit be carefully monitored, particularly in hypertensive patients, to prevent the development of complications associated with hypertension.