At the present time, there is limited information on the outcome of patients with acute lymphoblastic leukemia (ALL) who relapse after bone marrow transplantation (BMT). Intuitively, it might be expected that leukemia recurring after BMT would be refractory to further treatment. In an attempt to improve survival in patients with ALL who relapse after BMT, we used standard chemotherapy for reinduction and maintenance. Of 65 patients who relapse following allogeneic, autologous, or syngeneic BMT, 12 elected to receive no further chemotherapy, and their median survival from relapse was 36 days (range 13 to 167 days). The 53 patients who received therapy had a significantly longer median survival of 168 days (range 18 days to 4.7 years). With multidrug induction regimens there were 29 of 52 (56%) complete remissions. Six patients are currently alive, with two off therapy. In the patients who received therapy, the following factors were independent predictors of prolonged survival: longer time from BMT to relapse; younger age at diagnosis; and the use of a preparative regimen containing fractionated total body irradiation. In conclusion, leukemia recurring after BMT remains sensitive to standard therapy in many patients. We recommend that patients with ALL who relapse after BMT receive reinduction and maintenance therapy as additional good quality survival time is achieved in patients who attain a remission.