A 45-year-old male with chronic myelogenous leukemia received cryopreserved allogeneic bone marrow from his HLA-identical sister. Bone marrow was harvested and cryopreserved prior to chemoradiotherapy since the donor had neurotic tendencies. The preconditioning regimen consisted of standard dosage of busulfan plus cyclophosphamide and total lymphoid irradiation (5Gy). A total of 3.1 x 10(7)/kg marrow mononuclear cells, containing 4.7 x 10(5) CD34+ cells/kg, and 8.0 x 10(6)/kg buffy coat cells collected from the donor at day 0 was infused. Marrow engraftment occurred by day 38 although hematological recovery was delayed and subsequent administration of GM-CSF, methylprednisolone and donor buffy coat cells were required. Mononuclear cells obtained from the patient's blood at day 28 had an inhibitory effect on CFU-GM formation of the donor's bone marrow mononuclear cells. We considered that this case suffered from a transient myelosuppression due to residual host cells after bone marrow transplantation.