Between 30 and 50% of patients with acute myeloid leukaemia (AML) relapse after autologous stem cell transplantation (ASCT). One possibility of reducing the relapse rate could be the adoption of conditioning regimens specifically designed for AML. We report treatment results achieved with a new conditioning for ASCT, based on high-dose idarubicin (IDA) plus oral busulphan. Patients (n = 40) were conditioned with a regimen consisting of 3 d continuous intravenous infusion IDA at 20 mg/m2, followed by 4 d conventional dose oral busulphan. Unpurged peripheral blood stem cells were used in all cases. All patients had non-M3-AML and were in first complete remission (CR). The median number of CD34+ cells infused was 6.9 x 10(6)/l (2.6-24). No case of transplant-related mortality occurred. In all cases, left ventricular ejection fraction remained unmodified after ASCT. Thirty-three of 40 patients (82%) had grade 3-4 mucositis requiring total parenteral nutrition in all cases. After a median follow up for surviving patients of 32 months from ASCT, 30 patients (75%) are alive and 26 (65%) are in continuous CR. Our data show that a conditioning regimen based on high-dose IDA plus busulphan results in an encouraging reduction of the relapse rate after ASCT in AML.