BACKGROUND: In Asia, HSV seroprevalence studies are sparse and they have recorded lower prevalence of HSV infection, especially HSV-2. AIMS: To ascertain the seroprevalence of HSV-1 and HSV-2 in patients attending a STD clinic in a referral hospital in south India and to compare it with a control group. METHODS: The study included 135 consecutive STD cases having history of ulcerative or non-ulcerative STD in the present or in the past 5 years and 135 age and sex-matched controls. Diagnostic serology was done for HSV-1 and HSV-2 using type specific IgG by indirect immunoassay using ELISA. The results were analyzed utilizing Chi- square test. RESULTS: Amongst 135 STD clinic cases, 106 cases were males and 29 cases were females with male to female ratio of 3.65:1. The mean age was 32.2 years (range 16-65 years). Among study group cases, 112 (82.9%) cases were co-infected with HSV-1 and HSV-2, 11 (8.1%) cases were seropositive for HSV-1 alone and 3 (2.2%) cases were seropositive for HSV-2 alone. In the control group, 112 (82.9%) cases were co-infected with HSV-1 and 2, 12 (9.6%) for HSV-1 alone and 1(0.8%) for HSV-2 alone. Correlation of HSV-1 and HSV-2 serology with various demographic and behavioral factors was statistically insignificant. CONCLUSIONS: Seroprevalence of HSV-1 and HSV-2 in STD clinic cases and control group is high, similar to that recorded in sub-Saharan Africa. Thus, serological studies for HSV-1 and HSV-2 cannot be taken as a marker of sexual behavior in our set of population.