The transition from germ cell to embryo is an important event in the creation of new life. During this period, cells change their characteristics through changes in gene expression patterns. Histone methylation is considered to be a stable and important epigenetic marker regulating gene expression. In the present study, we investigated the expression of histone methyltransferases (HMTs) and histone demethylases (HDMs) during preimplantation development. Analysis by reverse transcription-PCR (RT-PCR) revealed that many of these enzymes are abundantly expressed in MII stage oocytes and that their expression levels change dynamically during preimplantation development. These results suggest that HMTs and HDMs are involved in the regulation of gene expression during preimplantation development.