Forty-four adults with AML (n = 18) or ALL (n = 26) beyond first remission underwent unpurged (n = 39) or purged (n = 5) autografting after 110-140 mg/m2 melphalan and 1050 cGy TBI. ALL patients were eligible to receive maintenance chemotherapy with 6-mercaptopurine and methotrexate for 2 years after hematologic recovery. The duration of first remission was 1-167 months (median 11). The median time to 50 x 10(9)/I platelets was 76 days, and that to 0.5 x 10(9)/I neutrophils 31 days. Eight patients died of transplant-related toxicity; seven within 1 year. Twenty-two patients relapsed at 1-20 months (median 2.5 months). The 3-year probabilities (95% CI) of relapse and disease-free survival are 58% (43-75%) and 31% (17-45%), respectively. The duration of the first remission (< 1 year vs > or = 1 year) and the stage of transplant (second remission vs other) had no effect on relapse or disease-free survival. There was a trend towards higher relapse rates (76 vs 34%) and poorer disease-free survival (19 vs 49%) among ALL patients compared with AML which did not reach significant levels due to small patient numbers. We conclude that melphalan-TBI is a suitable conditioning regimen for autografting in advanced leukemia. The outcome of AML patients is comparable to standard regimens, but the outcome of ALL patients is poor and measures to enhance the anti-leukemic efficacy are necessary.