We tested in vitro the effect of recombinant human erythropoietin (rhEPO) plus recombinant human G-CSF (rhG-CSF) on purified human CD34+ haemopoietic progenitors (HP) and in vivo in patients who had undergone anti-cancer chemotherapy for advanced ovarian cancer. In this preliminary experience we found that, in vitro, rhEPO potentiates the effect of rhG-CSF on HP growth and differentiation toward the granulocyte-macrophage lineage. rhEPO plus rhG-CSF produced in vitro a proliferative stimulus of HP which represents 26% of the maximum stimulation obtained using IL-1, IL-3, IL-6, G-CSF, GM-CSF and stem cell factor in combination. In the patients treated with rhEPO plus rhG-CSF after chemotherapy, we observed a favourable trend for platelet and neutrophil recoveries compared with a control group treated with rhG-CSF alone and a significantly higher haematocrit nadir was observed in the rhEPO plus rhG-CSF series. In the patients treated with rhEPO plus rhG-CSF we observed a significant increase of circulating colony-forming unit granulocyte-macrophage (CFU-GM) and burst forming unit-erythroid (BFU-e) compared with the rhG-CSF series. Our results, in vitro and in vivo, encourage the in vivo use of rhEPO plus rhG-CSF to improve blood cell recoveries of patients who have undergone conventional or high-dose chemotherapy. Moreover, rhEPO plus rhG-CSF was demonstrated to be a good HP mobilising treatment for blood stem cell collection after chemotherapy.