A retrospective study was undertaken to evaluate the efficacy of autologous blood stem cell transplantation (ABSCT) in terms of haemopoietic reconstitution after ablative chemotherapy or chemo-radiotherapy. 55 patients with malignancies, observed in four Italian institutions from January 1987 to June 1991, were eligible for evaluation. This series included 19 non-Hodgkin's lymphoma, 11 multiple myeloma, nine ovarian cancer, seven Hodgkin's disease, seven non-lymphocytic leukaemia, one acute lymphoblastic leukaemia, one neuroblastoma. 522 PBSC collections were performed on 55 patients. Following ABSCT, the rate of engraftment was positively related to the dose of CFU-GM infused and negatively to the presence of bone marrow involvement at conditioning. 48 patients out of 55 transplanted (87%) had rapid, complete and sustained engraftment. Three patients (5%) died of transplant-related complications. Considering that 60% of the patients in this series were in partial remission or in progressive disease at the time of ABSCT, we conclude that ABSCT is a safe approach for the use of ablative conditioning therapy in patients with a wide scope of malignancies, provided that a large number of CFU-GM have been collected after mobilizing treatment.