Abstract: Trichostatin A, a histone deacetylase inhibitor, could increase histone acetylation, and active gene expression in somatic cells. However, effect of TSA on histone methylation is unclear. In present study, the bovine fibroblast cells were treated with TSA, and histone acetylation and methylation were examined by using indirect immunofluorescence and scanning confocal microscopy. We found that the morphology of cells was changed from being slightly concave to more flat and elongated even at the 10 ng/mL group. Intensive H4K8ac signals in fibroblast cells were observed after TSA treatment. A similar increasing with H4K8ac in H3K4me3 was found, but no change was observed at H3K9me2 when somatic cells were treated with TSA. These result indicated that TSA was not only increasing histone acetylation, but also increasing histone methylation that was correlated with gene expression. However, TSA could not change the level of histone methylation that regulated gene silence.