Cryopreservation has been used extensively in autologous marrow transplantation (BMT), but there has been limited use in allogeneic BMT. We describe here 6 cases of successful engraftment following allogeneic BMT with cryopreserved marrow. Patients suffered from Wiscott-Aldrich syndrome, osteopetrosis, aplastic anemia, and acute lymphocytic, acute non-lymphocytic, and chronic myelogenous leukemia, and ranged in age from 5 mos to 35 yrs. Marrow was collected using standard techniques. In one case T-cells were removed to prevent graft-vs-host disease. Marrow was frozen for a variety of reasons. Buffy coat cells were frozen at controlled rate in 10% DMSO, and stored in liquid nitrogen for 6 to 49 d. Engraftment (WBC greater than 1000/uL x 3 d) occurred from 13 to 37 d post BMT. In 4 of 4 cases in which data are available, donor origin of engraftment was documented, 1 with cytogenetics, 2 with red cell typing, and 4 with restriction fragment length polymorphisms. 3 patients are alive and well 21, 21, and 42 months post BMT. These results suggest frozen marrow can be successfully used for allogeneic BMT.