Although intensive chemotherapy has improved event-free survival for most children with lymphoblastic leukaemia there remain up to 10% who have not benefited from this approach. These include infants, children with Ph1 positive leukaemia, with near-haploidy, and slow remitters in most of whom event free survival remains below 40%. Evaluation of the benefits of Bone Marrow Transplantation in high risk ALL is fraught with difficulties and to date has not produced clear evidence of benefit. The way forward lies in prospective evaluation of BMT in tightly defined subsets of highest risk children, a task which will require international collaboration.