We studied the therapeutic benefit of recombinant human erythropoietin (rHuEPO) in dialysis patients with thalassemia minor. Four of the 40 randomly selected patients (22 on hemodialysis [HD], 18 on continuous ambulatory peritoneal dialysis [CAPD]) were identified to be thalassemic prior to a trial of rHuEPO (alpha-thalassemia trait in three and beta-thalassemia minor in one). All patients were initially treated with rHuEPO at a dose of 100 +/- 25 U/kg/wk subcutaneously depending on the hemoglobin level. EPO injections were continued for 16 weeks with further adjustments of the doses according to the hemoglobin level increases attained. All nonthalassemic patients reached a target hemoglobin of 10 g/dL at week 16, with an average maintenance dose of 120 +/- 7.8 U/kg/wk, but the hemoglobin was increased by only 1 g/dL in the thalassemic patients receiving 175 U/kg/wk. Following cessation of rHuEPO therapy for 6 weeks, all four thalassemic patients and 18 randomly selected nonthalassemic patients received a fixed dose of rHuEPO 4,000 U/wk (equivalent to 80 U/kg/wk) for 16 weeks. The hemoglobin remained unchanged in the thalassemic patients, but a progressive and significant increase of hemoglobin was observed in the nonthalassemic patients. At the last phase of the study, the thalassemic patients received rHuEPO at a dose of 100 or 125 U/kg/wk with 4-weekly increments of 25 U/kg/wk until their hemoglobin reached 10 g/dL. One patient developed uncontrolled hypertension with a dose of 150 U/kg/wk, and one reached the target hemoglobin at a dose of 200 U/kg/wk.(ABSTRACT TRUNCATED AT 250 WORDS)