Aim: To investigate the possible role of HSV-Ⅱ in the etiology of atherosclerosis, the effects of herpes simplex virus type Ⅱ (HSV-Ⅱ ) infection on morphology and collagen synthesis of smooth muscle cells (SMC) were observed.Methods: Bovine aortic SMCs in culture were infected with HSV- Ⅱ, using 3H-proline incorporating into 3H-hydroxyproline by SMC as a criterion of collagen synthesis in SMC.Results: The significant cytopathic effect (CPE) such as cell rounding, swallowing, focal necrosis and detachrnent was observed 24 h after infection; there was a significant decrease in the synthesis of collagen in bovine SMC at 24 h, 36 h and 48 h after infection compared to controls.Conclusion: The results suggested that HSV-Ⅱmay be one of the injurious agents of inciting atherosclerosis by inhibiting collagen synthesis in SMC as well as injury factor for SMC.