The additional transplantation of ex vivo generated hematopoietic (post)-progenitor cells represents a possible approach to ameliorate high-dose chemotherapy induced cytopenia. We investigated the feasibility of the large-scale expansion and transplantation of autologous megakaryocytic cells in four patients with advanced solid tumors. Up to 1,460x10(6) ex vivo generated cells were administered without adverse effects but no clear cut effect on platelet recovery was observed.