The hematologic response of 65 continuous ambulatory peritoneal dialysis (CAPD) patients to subcutaneous recombinant human erythropoietin (rHuEPO) was compared with that of 369 hemodialysis patients (HD). Pretherapy transfusions were more common in HD than CAPD. The response was measured as the change in hematocrit after 70 or more days of therapy (or as the hematocrit change normalized by a weekly dose) in CAPD patients. The weekly rHuEPO dose did not differ, but the dosing frequency was less in CAPD than in HD patients. Hematologic response parameters were greater in CAPD. Multivariate analysis showed that the response in both groups varied inversely with the frequency of dosing and with pretherapy baseline hematocrit. In HD subjects, the response also varied inversely with previous transfusion history. The authors concluded that CAPD patients responded better to rHuEPO than HD patients. This may be a result, in part, of lower ongoing blood losses. Patients with more severe anemias responded less well, whereas more sensitive patients were dosed less frequently.