Our objective was to evaluate the seroprevalence of herpes simplex virus (HSV)-2 and HSV-1 in a population of men and women attending the STD clinic of Hôpital St-Louis (Paris, France). Four hundred and eighty-seven patients (264 men and 223 women) were tested for HSV-2 and HSV-1 antibodies by specific enzyme immunoassay (EIA) (Smithkline-Beecham Biologicals). Univariate and multivariate analyses were carried out for correlations with clinical, socio-epidemiological and behavioural data. HSV-2 seroprevalence was 55% (44.7% in men, 67.3% in women). HSV-1 seroprevalence was 93% (94.7% in men, 91% in women). The predictive factors of HSV-2 seropositivity being female (OR: 3.37), age (OR: 1.04), country of origin (Central Africa OR: 3.52, North Africa OR: 1.36), history of genital herpes (OR: 10.97), hepatitis B virus (HBV) markers (OR: 1.92) and hepatitis C virus (HCV) markers (OR: 3.96). The only protective factor was HSV-1 seropositivity (OR: 0.25). The predictive factors of HSV-1 seropositivity were only the country of origin (Central Africa OR: 2.95, North Africa OR: 1.83) and the absence of genital herpes (OR: 11.01). Only 23 (8.6%) HSV-2 seropositive patients had a history of genital herpes. This study underlines the very high HSV-2 seroprevalence of patients with STDs, only a few of whom have a history of genital herpes. Detection and counselling is urgently needed for these patients.