The administration of recombinant human erythropoietin (rHuEPO) in CAPD patients is usually done subcutaneously. Only a few authors have reported on its intraperitoneal (IP) administration. We compared the effect of IP administration of rHuEPO in CAPD patients to that of intravenous (IV) administration. Ten anemic CAPD patients injected rHuEPO into their dialysis bag once a day, 3 times a week, for 18 weeks. The initial dose was 12,000 U. The dwell time of the exchanges with rHuEPO was about 6 hours. Nine other anemic CAPD patients were treated with IV rHuEPO once a week for 18 weeks. The initial dose was 6000 U. In the IP group the hematocrit rose from 24.04 +/- 2.7% to 33.3 +/- 3.8% (mean +/- SD). In the IV group 2 patients were excluded from the efficiency evaluation. In 7 of the 9 patients in the IV group, the hematocrit rose from 23.27 +/- 2.6% to 32 +/- 5.5% (mean +/- SD). The intraperitoneal administration of rHuEPO in CAPD patients is sufficient in improving anemia, although it requires a much larger dosage to yield the same level of improvement as the one obtained with the intravenous administration. However, in patients on continuous cycling peritoneal dialysis or IP dialysis, a smaller dosage during the prolonged dwell time may be effective.