Fifty-two patients with acute lymphoblastic leukemia (ALL) underwent allogeneic bone marrow transplantation following cytoreduction with total body irradiation and cyclophosphamide. Twenty-two patients were in second remission, 15 in a later remission, and 15 were in relapse at the time of the transplant. At a median follow-up of 24 mo, 14 of those in second remission survive in continuous remission compared to 5 in later remission and 4 in the relapse group. Statistical analysis showed an improved disease-free survival for the second remission group (p = 0.09). Patients transplanted in later remission or relapse had a similar survival. The improved survival in second remission resulted from a decreased relapse rate posttransplant, as the early mortality from nonleukemic causes was similar among the groups (p = 0.01). In the second remission patients, no characteristics of the initial leukemia were identified that significantly affected outcome. In the combined later remission and relapse group, poor prognosis posttransplant was associated with initial WBC greater than 20K, age at diagnosis older than 10, or initial remission duration less than or equal to 1 yr. These results suggest that extended disease-free survival may be achieved by second remission transplantation and that improved therapy is necessary for later remission or relapse transplants due to the high rate of posttransplant relapse.