To examine the possible role of HCMV in the etiology of atherosclerosis, we searched for the presence of HCMV DNA in arterial vascular tissues by in situ hybridization. Biotin labelled HCMV DNA probe was used on specimens of arterial wall taken from patients with clinically significant atherosclerosis. Evidence for the presence of HCMV DNA was obtained in 13 specimens out of 32 atherosclerosis specimens. In contrast, only 1 specimen was positive in the control group (Total 15 specimens of normal arterial and venous wall), suggesting that there is a close relationship between human cytomegalovirus infection and atherosclerosis development. The results also showed that the positive hybridization signals were mainly observed in the nuclei of smooth muscular cells, rarely found in outer layer of arterial walls, cell membrane and cytoplasm. It was indicating that HCMV infection might be an etiological agent in the development of atherosclerosis.