Recombinant human erythropoietin (EPO) has been used for 4 years in end-stage renal disease patients, administered intravenously 3 times a week. A study was undertaken to determine the optimal way of administration comparing 3 times weekly intravenous EPO to self-administered daily subcutaneous EPO (SADSCEPO). In a first group of 4 patients, we demonstrated that the change from 3 times weekly intravenous EPO to SADSCEPO permitted a dose reduction of 70%. In a second group of 20 patients who started the EPO therapy with the daily subcutaneous route at a median dose of 12 U/kg/day, the hematocrit increased from 20 to 30% in 4 months and remained over 30% in spite of a median dose reduction to 9 U/kg/day. The patients' acceptance of SADSCEPO was good. The mechanism allowing such a dose reduction is unknown. However, the significant reduction in median dosage requirement with the subcutaneous route should allow a greater number of patients to be treated more cost-effectively.