To evaluate efficacy, safety, changes in biological features, and quality of life (QoL) in low-risk anemic patients with MDS treated with darbepoetin alfa (DPO), 41 patients received DPO 150 microg weekly for 24 weeks. The dose was increased to 300 microg weekly in non-responsive patients. During treatment, 10/17 (59%) transfusion-dependent (TD) and 13/23 (56%) transfusion-free (TF) patients responded. In TF patients, Hb increased from 9.2 +/- 0.9 g/dL to 10.3 +/- 1.4 g/dL by 24 weeks (p = 0.004). The mean response duration was 22 weeks (95% CI: 19.7-24.0) in TF patients compared with 15.1 weeks (95% CI: 13.3-17.5) in TD patients. Response to treatment was associated with increases in QoL. Decreases in the percentage of apoptotic progenitor cells (p = 0.007) and CD34+ cells (p = 0.005) were observed. These results confirm previous studies demonstrating the safety and efficacy of DPO in anemic patients with MDS. Biological changes and improvement in QoL were associated with response. Adequate dosing is to be determined.