Recent research has highlighted the risk of HIV infection for married teenage women compared with their unmarried counterparts (Bruce and Clark, 2003; Clark, 2004). This study examines for post-adolescent women age 20-29 in Cameroon whether a relationship exists between HIV status and age at first marriage, or the length of time between first sex and first marriage. Multivariate analysis using the nationally representative sample from the 2004 Cameroon Demographic and Health Survey shows that late-marrying women and those with a longer period of premarital sex have the highest risk of contracting HIV. Although, overall, women in urban areas marry later than their rural counterparts, the positive relationship between HIV risk and age at marriage is stronger in rural areas. For late-marrying women, living in households with higher wealth status and having a larger number of lifetime sexual partners contribute to higher HIV risk. Given that age at first marriage and the gap between first marriage and first sex have increased in recent years, focusing preventive efforts on late-marrying women will be important in reducing HIV prevalence among females.