The results of allogeneic marrow transplantation in 75 patients with acute lymphoblastic leukemia and 63 patients with acute non-lymphoblastic leukemia in relapse are reviewed. The effects of various chemotherapeutic regimens added to the basic regimen of cyclophosphamide (Cy) 60 mg/kg given on each of two successive days followed by 1000 rad of total body irradiation (TBI) were evaluated. The regimens tested were dimethylbusulphan (DMB), 1,3-bis(2-chlorethyl)-1-nitrosourea (BCNU) and daunorubicin. Seventeen of 138 patients are alive between three and nine and a half years from transplantation. The addition of other chemotherapeutic agents to th basic Cy and TBI regimen did not decrease relapse frequency or prolong survival.