* Imatinib inhibits the breakpoint cluster region-Abelson (BCR-ABL) tyrosine kinase, which is produced by the chromosomal abnormality known as the Philadelphia (Ph) chromosome in patients with Ph chromosome-positive acute lymphoblastic leukaemia (Ph+ ALL). * The clinical efficacy and safety of oral imatinib in patients with relapsed or refractory Ph+ ALL has been demonstrated in a noncomparative, open-label phase II trial (n = 48) and an expanded-access study (n = 353). The majority of patients received imatinib 600mg once daily. * In the phase II trial, imatinib induced complete haematological responses in 19% of patients, marrow complete responses in 10% of patients and partial marrow responses in 31% of patients. These were sustained for at least 4 weeks in 27% of patients. * The estimated median times to progression were 2-3.1 months in the phase II trial, the expanded-access study and a population of 68 patients pooled from these studies, with estimated median overall survival rates of 4.9-9 months. * In 22 patients receiving imatinib prior to undergoing allogeneic stem cell tranplantation (SCT) in the phase II trial and expanded-access study, estimated disease-free survival and overall survival rates 12 months after SCT were 25.5% and 44.8%. * Although adverse events were frequent among relapsed or refractory Ph+ ALL patients treated with imatinib, the majority of non-haematological adverse events were mild or moderate in severity.