High-dose chemotherapy with autologous transplantation of in vivo purged PBSC is a new and interesting therapeutic option for CML patients not eligible for allogeneic transplantation. We investigated the feasibility and toxicity of this approach in 57 patients with Ph-positive CML. For mobilization of Ph-negative PBSC, patients were treated either with '5 + 2/7 + 3'- type chemotherapy or with 'mini-ICE/ICE' chemotherapy followed by administration of G-CSF. Fourteen patients were in early chronic phase, 30 patients in late chronic phase and 13 patients in accelerated phase (AP) or blast crisis (BC). Cytogenetic responses in the PBSC harvests were dependent on both disease stage and type of chemotherapy: in late chronic phase and AP/BC, a complete or major cytogenetic response could be obtained in nine out of 13 patients treated with 'mini-ICE/ICE' but only in three out of 23 patients treated with '5 + 2/7 + 3' chemotherapy. However, in early chronic phase a Ph-negative autograft could be obtained in three out of eight patients upon mobilization with '5 + 2' chemotherapy. Thirty-one patients underwent PBSC transplantation and all of them successfully engrafted. Post-transplant cytogenetic analysis was available on 21 cases, of whom seven achieved a complete or major cytogenetic response, with two minor cytogenetic remissions. One patient (1/57) in blast crisis died during mobilization therapy (1.8%). Transplantation related mortality was 0%. This study demonstrates that mobilization of Ph-negative PBSC after myelosuppressive chemotherapy is feasible in CML patients and is associated with acceptable toxicity. Autologous transplantation of in vivo purged PBSC is a safe procedure with rapid and complete hematopietic recovery.