We have investigated the feasibility and efficacy of administering a radiation-free preparative regimen in the setting of allogeneic bone marrow transplantation (BMT) in 40 consecutive patients with acute lymphoblastic leukaemia (ALL). Busulfan (4 mg/kg/d x 4 d) and cyclophosphamide (50 mg/kg/d x 4 d) (BuCy4) were given in 29 patients and 11 received busulfan (4 mg/kg/d x 4 d), etoposide (60 mg/kg) and cyclophosphamide (60 mg/kg/d x 2 d) (BuCy+VP - 16). Median age was 22 years (range 1-50); 11 patients were children < or = 15 years of age. All children and 20 adults were at high risk of relapse pretransplant. Nine adults and one child died from transplant-related toxicity. 11 patients relapsed at a median of 11 months post-transplant (range 2-27). The 3-year Kaplan-Meier estimated probability of relapse was 42.1% and found to be significantly lower in patients with chronic GVHD (P = 0.03). 19 patients are leukaemia-free survivors with a median follow-up of 33 months (range 7-59). The Kaplan-Meier actuarial probability of disease-free survival at 3 years was 43% for all patients. 63.6% for children versus 30.2% for adults (P = 0.24) and 51.6% for patients transplanted in first remission versus 30.2% for those transplanted in subsequent remissions (P = 0.20).