Twice weekly subcutaneous (s.c.) administration of recombinant human erythropoietin (rHuEPO) is effective in reversing renal anemia in CAPD patients. However the optimal frequency of administration has not been established. It would be more convenient to give rHuEPO by once weekly rather than twice weekly injection. We have therefore compared the effect of twice weekly versus once weekly s.c. administration of rHuEPO. Two groups of 10 CAPD patients were given the same starting dose of s.c. rHuEPO (100 U/kg body wt/week) either as a single weekly dose or twice weekly in divided doses. The rHuEPO dosage was then adjusted according to the hematologic response. The aim was to increase hemoglobin levels by about 1 g/dl per month. The target hemoglobin was 10 g/dl. After 16 weeks of treatment with rHuEPO, the hemoglobin levels rose from 6.6 +/- 1.2 (mean +/- SD) to 10.1 +/- 1.1 g/dl in the once weekly group and from 6.4 +/- 0.8 to 10.2 +/- 1.1 g/dl in the twice weekly group. The average doses of rHuEPO used during the study were 84 +/- 16 and 88 +/- 15 U/kg body wt/wk for the once weekly and twice weekly groups respectively. Subcutaneous administration of low dose rHuEPO is effective in reversing renal anemia. Similar responses were obtained with once weekly and twice weekly regimens. It is therefore acceptable and convenient for patients to receive one weekly s.c. injection of rHuEPO for the treatment of renal anemia.