In a phase I/II study, 47 patients (median age, 24 years) with hematologic malignancies (33 patients with acute leukemia not in first remission and 14 patients with other advanced malignant hematologic disorders) were treated with total body irradiation and high doses of etoposide (VP16-213) followed by bone marrow transplantation. At the time of analysis, 21 patients were alive, and 19 of them were in continued complete remission for 101 days to greater than 40 months (median, 12 months). The actuarial disease-free survival rate of the 33 acute leukemia patients is 43% (2 SEM, 18%) and the actuarial relapse rate is 32% (2 SEM, 20%). Five of the 14 patients with the other hematologic malignancies are alive, and four of them continue to be free of disease for 8 to 27 months. Pharmacokinetic studies established a strong correlation between the administered drug doses and their plasma levels and also demonstrated complete drug clearance prior to marrow grafting. An etoposide dose of 60 mg/kg body weight was found to be the maximum tolerated dose. This new preparatory regimen was well tolerated and was not associated with specific acute or long-term regimen-related toxicities. Our data suggest that total body irradiation with high-dose etoposide presents a viable alternative to other preparatory regimens. The role of this novel combination remains to be defined by future prospective randomized trials.