One hundred and sixteen (116) anaemic patients with myelodysplastic syndromes (MDS) were treated with recombinant human erythropoietin (r-HuEpo) in an openlabel, multicentre, compassionate treatment trial; 100 patients received therapy for ≧ 4 weeks and were evaluable for efficacy. The distribution of FAB subtypes was: 44 RA, 40 RARS, eight RAEB, two RAEB-t, one CMML, and five not specified. Mean baseline haematocrit was 24.5%, and the mean prestudy transfusion requirement in the 12 weeks immediately prior to study entry was 6.5 units. r-HuEpo treatment was initiated at a dose of 150U/kg three times weekly, with dose escalations of 50U/kg monthly (up to 300U/kg 3 x /week) permitted if the haematocrit failed to rise. Response to therapy was defined as either an increase in haematocrit of ≧ 6 percentage points over baseline, unrelated to transfusion, or a ≧ 50% decrease in transfusion requirement in the last 3 months of study treatment, compared to the baseline period (12 weeks), By these criteria, 28% (28/100) of patients responded to r-HuEpo treatment. Overall, 86% (24/28) of patients responding to therapy had baseline Epo levels ≧ 100 mU/ml. Response rates by FAB subtype were: RA 39% (17/44), RARS 17.5% (7/40) and RAEB 12.5% (1/8). Additionally, a 54% (15/28) response rate was seen in RA patients with baseline EPo levels ≧ 100 mU/ml. Responses to therapy were durable and generally occurred at r-HuEpo doses of 150-200 U/kg t.i.w. There were no reports of thrombosis, seizures or therapy-related hypertension. The data show that patients with MDS, especially those with the RA and RARS subtypes, can benefit from treatment with r-HuEpo. Those patients with baseline Epo levels ≧ 100 mU/ml were most likely to respond to therapy.