Mobilization and transplantation of peripheral blood progenitor cells (PBPCs) was investigated in patients with stage IA or stage IIA chronic myelogenous leukaemia (CML) using combination chemotherapy with idarubicin, cytosine arabinoside and etoposide (ICE) followed by simultaneous administration of rhG-CSF and rhIL-2 or rhG-CSF alone. 17 patients (stage IA: 12; stage IIA: five) were mobilized. Chemotherapy, cytokine priming and collection of PBPCs were well tolerated. Using large-volume aphereses, a median number of 10.6 x 10(7)/kg b.w. of MNC were harvested, which yielded between 0.15 and 21.0 x 10(6) CD34+ cells/kg b.w. High numbers of CD34+ HLA-DR- cells could be obtained. Autologous transplantation of mostly Ph- apheresis products was performed in 16/17 patients after high-dose chemotherapy, 10 patients achieved a complete or major cytogenetic remission (stage IA: seven; stage IIA: three), but six patients did not respond cytogenetically. Median follow-up after transplantation was 18+ months. Our data show that this very efficient treatment modality for PBPC mobilization in CML was safe and able to induce major and sustained cytogenetic responses in the majority of patients.