Bone marrow harvested from two previously treated patients was cryopreserved prior to their first dose of Methyl CCNU. The thawed bone marrow was reinfused 96 hours after a subsequent dose of MeCCNU in one patient after the previous dose caused severe myelosuppression. In the other patient, the bone marrow was given 96 hours after an escalation of the MeCCNU dose. In both patients, myelosuppression was abrogated and viable stem cells were recovered in the peripheral blood.