Myelodysplastic syndromes (MDS) are a group of clonal haematological disorders with a highly unfavourable prognosis. Allogeneic bone marrow transplantation offers the sole possibility for cure and prolonged survival, but is only available for a minority of patients. Therefore, we investigated the feasibility of PBPC collection and transplantation in 11 patients with high-risk myelodysplasia who were not eligible for allogeneic bone marrow transplantation. In six patients, PBPC were harvested after mobilization with G-CSF alone. Five patients were harvested during the recovery phase of intensive chemotherapy combined with G-CSF. This resulted in seven patients in an adequate CD34 progenitor yield > 1 x 10(6)/kg. Six patients obtained a CFU-GM content of the PBPC harvest > 10 x 10(4)/kg. Five patients were subsequently transplanted following a standard BuCy4 regimen. The median to ANC (absolute neutrophil count) > or = 0.5 and 1.0 x 10(9)/l was respectively 14 d (range 10-18) and 16 d (range 11-25). Platelets were self-supporting > or = 20 x 10(9)/l after a median of 41 d (ranges 8-144). One patient had a persistent lack of platelet engraftment unresponsive to infusion of back-up bone marrow. These data demonstrate that in selected patients with high-risk MDS, adequate PBPC collection appears feasible, enabling the harvest of sufficient cell numbers required for rapid and stable engraftment after reinfusion. Improvement in mobilization efficiency may enable the collection of higher CD34+ progenitor cell numbers required for more rapid platelet engraftment. PBPC transplantation may be an alternative treatment option for patients who lack an allogeneic marrow donor. Follow-up is, however, still too limited to draw any conclusion regarding the long-term cure rate.