To study whether gene IGSF4 was inactived by methylation in leukocytic cells, expression of IGSF4 was examined before and after treatment with demethylating agent in U937, Molt4 and HL-60 leukemia cell lines by means of RT-PCR. The methylation of promoter in U937, Molt4 and HL-60 cells as well as 21 acute leukemia patients was analyzed by MS-PCR. The results showed that methylation of IGSF4 promoter was inactived and could be reversed by treatment with a demethylating agent in U937, Molt4 and HL-60 cell. IGSF4 promoter methylation was detected in 57.1% of acute leukemia patients. There is no difference in incidence of IGSF4 promoter methylation between acute myelocytic leukemia and acute lymphocytic leukemia. In conclusion, IGSF4 is frequently inactived in acute leukemia and is a good candidate for the leukemia suppressor gene. As a normal suppressor gene, it may play an important role in inhibiting the development of leukemia, and the methylation of gene IGSF4 may be a good index in monitoring relapse of leukemia.