Introduction Globally Herpes Simplex Virus Type-2 (HSV-2) is amongst the most common sexually transmitted infections. 1 HSV-2 seroprevalence studies show variation in infection by geographic location. The highest prevalence levels of the virus have been found in Africa and the Americas. Although there have been few studies, the lowest prevalence has been seen in Asia. 2 Herpes Simplex Virus has been characterized into 2 distinct serotypes; HSV-1 and HSV-2. HSV-2 is primarily associated with genital and neonatal infections. Global research evidence has shown that there is a link between the HIV epidemic and the herpes simplex virus (HSV-2) infection. 3 Amongst all sexually transmitted infections there appears to be a true epidemiologic synergy between these two viruses. 4 Recent evidence accumulated from Africa, Asia and the Americas shows that the impact of genital HSV infection has increased the risk of HIV acquisition. 5 HSV-2 prevalence has been found to vary by individual-level characteristics with the risk of acquisition being influenced by factors such as gender, age, sexual activity level, marital status, socioeconomic status (SES), education, race and ethnicity. 6 Till recently, we did not have either national or city wise prevalence estimates for HSV infection in Pakistan. In 2007 the Ministry of Health and the National Aids Control Program (NACP) commissioned a behavioural and biological study of urban male population that was implemented by the Population Council. The two main objectives of this DFID- funded study were to estimate the prevalence of five commonly occurring STIs, including HIV, in six major cities of the country and to document sexual behaviours amongst urban male population. This paper discusses results related to the prevalence of HSV-2 infection amongst males in the six major cities of Pakistan. Materials and Methods The main component of the study was a cross- sectional behavioural and biological survey of 2400 men carried out in six major cities of Pakistan from June to August 2007. Only male population were selected as they constitute the bridging population that is a conduit for the spread of sexually transmitted infections from high to low risk general population. City selection was based on inclusion of the four provincial capitals of the country, Lahore, Peshawar, Quetta and Karachi as well as two other larger cities, Rawalpindi and Faisalabad. A multistage sampling design was employed to select a total of 400 men aged 16-45 years in each city. In the first stage 10 blocks demarcated by the Population Census Organization (that comprise 200-250 households) were Vol. 60, No. 11, November 2010 918 Original Article Herpes Simplex Virus-2 infection amongst urban male population in Pakistan Ali Mohammad Mir, Abdul Wajid, Laura Reichenbach, Mumraiz Khan, Irfan Masood Population Council, House 7, Street 62, F-6/3, Islamabad, Pakistan. Abstract Objective: To describe the prevalence of Herpes Simplex Virus-2 (HSV-2) infection among males in six major cities of Pakistan. Methods: A cross sectional behavioural and biological survey of urban male population aged 16-45 years was conducted in Rawalpindi, Lahore, Karachi, Faisalabad, Peshawar and Quetta to measure the prevalence of five sexually transmitted infections and assess sexual behaviours. Respondents were selected through a multistage sampling technique. In each city 10 blocks demarcated by the Population Census Organization were selected based on probability proportional to socio-economic status. In each block 40 men were selected through systematic sampling with a random start. In total 2400 men were administered a behavioural questionnaire and 2396 provided biological specimens for laboratory testing. Results: This paper discusses the overall and city wise prevalence of HSV-2 infection. The overall prevalence of HSV-2 infection in the six cities was 3.4 percent (95% CI 2.8-4.3). City wise the highest prevalence was reported in Karachi 6 percent (95% CI 4.1-8.8), followed by Lahore and Quetta at 4.3 percent (95% CI 2.7-6.7), and Faisalabad at 2.5 percent (95% CI 1.4-4.5). The lowest prevalence was in Rawalpindi at 1.8 percent (95% CI 0.9-3.6). Conclusion: Empirical evidence from this study suggests that there is city wise variation in the prevalence of HSV- 2 infection across the major cities in Pakistan. Based on possible link between HSV-2 and HIV, future HIV control strategies must also focus on the better management of HSV-2 infections in Pakistan (JPMA 60:918; 2010).