Seven of 11 patients with acute myeloblastic leukemia (AML) had allele(s) in which more than half of 27 CpG sites in the p15 gene were methylated. The p15 CpG island region was surrounded with both the acetylated histone H3 (AcH3) and dimethylated histone H3-lysine 9 (MeH3K9) in bone marrow cells of AML patients, whereas with AcH3 alone in normal marrow cells. The p15 CpG islands of DNA immunoprecipitated with anti-AcH3 antibody and anti-MeH3K9 antibody were not always unmethylated and methylated, respectively, in the patients. These results suggest perturbed modifications of histone H3 around the p15 CpG island region in AML.