It has been found recently that di-n-butyl phthalate (DBP) possesses a new pharmacological activity in the selective elimination of tumor cells from marrow. In combination with long-term liquid culture of marrow cells in vitro, DBP purged autologous bone marrow transplantation has first been applied to a case of acute myeloid leukemia at the first complete remission with successful reconstitution of hematopoiesis.