The purpose of this study was to evaluate the outcome of children with acute lymphoid leukemia (ALL) in second remission who have undergone high-dose chemotherapy and radiotherapy and autologous bone marrow transplantation (ABMT) with monoclonal antibody purged marrow, and to determine the main prognostic factors. From 1987 to 1992, 55 children with ALL in second remission underwent ABMT. The conditioning regimen consisted of total body irradiation (TBI) plus cyclophosphamide in 21 patients and TBI plus cyclophosphamide plus cytarabine or VP-16 in 28 patients; the remaining six patients were treated with chemotherapy alone (cyclophosphamide and busulfan, and/or VP-16). The marrow was purged using monoclonal antibodies and complement or magnetic microspheres in all cases. All patients engrafted. Three patients (5%) died early post transplant from infections. Twenty-six patients (47%) relapsed (median 150 days); 26 patients (47%) are alive and in complete remission (CR) at a median of 36 months. The Kaplan-Meier estimation showed a probability of event-free survival (EFS) of 46 +/- 0.007%. In the univariate analysis, first CR length and conditioning with TBI plus two or more cytotoxic drugs were found to be the most significant predictors of EFS. ABMT with purged marrow is a treatment modality which offers a chance of cure in children with ALL after relapse, including children who relapse early.