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Abstract Backgrounds and objectives: Herpes simplex virus type 1 (HSV- 1) infections are mostly shown as a Herpes disease, but It causes conjunctivitis, genital herpes, encephalitis and newborn herpes. This study was conducted to determine the sero-epidemiologic prevalence of herpes simplex virus type 1 in cases referred to clinical laboratories of Gorgan, Iran. Material and methods: In this cross sectional study, we did random blood sampling on 406 cases referred to the Gorgan city's clinical laboratories. These samples were analyzed for HSV-1 Immunoglobulin G and M antibodies using type- specific enzymelinked Immunoassays (ELISA). Results: Of 406 participants, the HSV-1 seroprevalence is 49% (44.3% and 4.7% for IgG and IgM respectively). There is not significant relationship between seropositive HSV-1 and gender, ethnicity, age and marital status. Conclusion: Sero-epidemiological of HSV-1 in Gorgan is the same of the other places in Iran, but it is higher than European and lower than African countries. It seems that the people’s culture is very important. Therefore it needs to be investigated more. Keywords: HSV-1, Antibody, Gorgan.