To evaluate the molecular events in the genome that are associated with myelodysplastic syndromes (MDS) and the development of leukemia, we investigated the expression of the deleted in colorectal carcinoma (DCC) gene by the reverse transcriptase-polymerase chain reaction (RTPCR) method in 24 MDS cases and in 7 overt leukemia cases that progressed from MDS. Expression of the DCC gene was absent or extremely reduced in 2 of the 24 MDS cases, and those 2 cases developed overt leukemia within 6 months. Moreover, in 5 of the 7 cases of overt leukemia that developed from MDS, expression of the DCC gene was absent or extremely reduced. These findings suggest that inactivation of the DCC gene may be the late event that triggers the progression of MDS to leukemia.