Background & objectives: There are sparse data on the prevalence of primary infertility in India and almost none from Southern India. This study describes the correlates and prevalence of primary infertility among young women in Mysore, India. Methods: The baseline data were collected between November 2005 through March 2006, among 897 sexually active women, aged 15-30 yr, for a study investigating the relationship of bacterial vaginosis and acquisition of herpes simplex virus type-2 (HSV-2) infection. A secondary data analysis of the baseline data was undertaken. Primary infertility was defined as having been married for longer than two years, not using contraception and without a child. Logistic regression was used to examine factors associated with primary infertility. Results: The mean age of the women was 25.9 yr (range: 16-30 yr) and the prevalence of primary infertility was 12.6 per cent [95% Confidence Interval (CI): 10.5-15.0%]. The main factor associated with primary infertility was HSV-2 seropositivity (adjusted odds ratio: 3.41; CI: 1.86, 6.26). Interpretation & conclusions: The estimated prevalence of primary infertility among women in the study was within the range reported by the WHO and similar to other estimates from India. Further research is needed to examine the role of HSV-2 in primary infertility.