Coordination of marrow donation for allogeneic BMT is a common logistical problem. The use of cryopreserved donor marrow would facilitate scheduling and avoid potential problems due to donor employment, injury, infection or death. We analysed results of 10 matched related BMTs performed with cryopreserved donor marrow and compared them with 33 matched related BMTs using fresh bone marrow over a 4 year period. No difference in time to engraftment of granulocytes and platelets or transfusion requirements were demonstrated for the two groups. However, there was less GVHD in patients who received cryopreserved donor marrow (chi 2, p = 0.03; Fisher's exact test (two-sided) p = 0.067) despite comparable risk factors. The reason for this difference is unclear. Our results indicate that the use of cryopreserved bone marrow for allogeneic BMT patients is at least equivalent to the use of fresh bone marrow. A prospective randomized trial is needed to determine if a true difference exists in the incidence or severity of acute GVHD and to determine if recurrence rate is different between the two groups.