Background: Genital herpes, a sexually transmitted disease caused by herpes simplex virus type 2 (HSV-2), is found in 3.8% of all sexually transmitted diseases (STD) in Chile. Aim: To determine the seroprevalence of herpes simplex virus type 2 (HSV-2) and to identify an association between HSV-2 and HIV-1, other STD, and to study its demographic characteristics. Material and methods: A cross-sectional study at two STD public clinics in Santiago was conducted among 200 consecutive patients. Samples were tested for HSV-2, HIV-1, syphilis and hepatitis B virus surface antigen. Results: The seroprevalence for HSV-2 was 43%. Four patients had a history of genital herpes. There was a strong association between HSV-2 infection and HIV-1 positivity (OR=8.7, 95% CI 3.4-22.4, p <0.001) and the condition of being a sexual worker (OR=4.5, 95% CI 1.7-11.9, p <0.01). Conclusions: The high association with HIV-1 and sexual workers, emphasizes the need of having HSV-2 specific diagnostic tests, counseling on sign and symptom recognition and taking preventive measures (Rev Méd Chile 2005; 133: 302-6)