Women in India suffer from a high incidence of reproductive disease, disability and death. Very little work has been done on men, but a much higher incidence of sexual experience outside marriage and sexually transmitted diseases (STDs) among males than previously expected for this population is now being documented. In north India, women are dependent on their husbands and other family members for health-related decisions. Therefore, the behaviour, knowledge and attitudes of men are integral to the reproductive health status of couples there. This study explores knowledge about three distinct areas of reproductive health among 6549 married men in five districts of the northern state of Uttar Pradesh, India. Factors contributing to men's knowledge in the areas of fertility, maternal health and STDs were investigated. Results showed that very few men had basic knowledge in any of these areas. The likelihood of reporting knowledge was associated with a set of determinants that differed in their magnitude and effect across the areas of reproductive health explored. In particular, men's belief about the ability of an individual to prevent pregnancy demonstrated an independent association with men's knowledge. After controlling for factors such as age, parity and educational and economic status, men who believed it not possible to prevent a pregnancy were less likely to know when during the menstrual cycle women would become pregnant and certain facts about STDs, but they were more likely to be able to name two or more symptoms of serious maternal health conditions. Possible explanations for this trend are discussed.