Seventeen patients who had a relapse at a median of 9 months after marrow transplant (14 allogeneic and three syngeneic) received second transplants. Eight patients were in remission when transplanted. Of the nine patients with active disease at the time of transplant, six had complete remissions, and one converted from blastic to chronic phase of chronic myelogenous leukemia. The median survival was 9 months (95% confidence interval, 4 to 17 months). Four patients died within 100 days of transplantation, and three were disease-free. Ten patients died after 100 days, all except two of disease relapse. Five patients had remissions that were greater than 12 months and longer than the remission after their first transplant (inversions). Three patients remain alive and disease-free at 37+, 55+, and 61+ months, the former two despite remissions of less than 1 year after their first transplant. Second transplants with a different cytoreductive regimen can eradicate disease resistant to prior myeloablative treatment; some patients may benefit from second transplants, even if the first transplant only achieves a short remission.