We report four patients (mean age 65 yr; range 40-77 yr) affected by acquired pure red cell aplasia (PRCA) complicating chronic lymphoid disorders and treated with anti-CD20 monoclonal antibody rituximab. Three out of four patients were given packed red cell transfusion. Steroids and recombinant erythropoietin (r-Epo) were also administered as first-line therapy without response. After a mean time of 57 d (range 23-62 d) from PRCA diagnosis, all patients received rituximab at a dosage of 375 mg/m(2)/wk for four consecutive weeks. First injection side effects of rituximab were minimal. All patients showed an increase in hemoglobin levels in response to rituximab, in one patient just after the first dose, in another patient after the second and in two other patients after the third dose. Three patients (75%) were considered in complete remission (CR) and one patient (25%) in partial remission 4 wk after the last rituximab infusion, despite a CR was obtained later (16 wk following the beginning of the therapy). Finally, at the last follow-up (mean 18.5 months, range 2-60 months), all patients were alive and in continue CR. Despite very limited in number, these results suggest that rituximab is very effective in the treatment of PRCA complicating B-cell chronic lymphoproliferative disorders.