BACKGROUND Our aim was to examine the association between use of alcohol and subsequent incidence of primary infertility. METHODS The study subjects were chosen from a population-based cohort of Danish women aged 20-29 years. Eligible women were nulliparous and not pregnant (n = 7760). Information on alcohol intake and potential confounders (age, education, marital status, diseases in the reproductive organs, and cigarette smoking) was assessed at enrollment. The incidence of fertility problems during follow-up was obtained by record linkage with the Danish Hospital Discharge Register and the Danish Infertility Cohort Register. Main outcome measures were hazard ratios of infertility according to alcohol intake at baseline estimated in a multivariate Cox proportional hazards model. RESULTS During a mean follow-up of 4.9 years, 368 women had experienced infertility. Alcohol intake at baseline was unassociated with infertility among younger women, but was a significant predictor for infertility among women above age 30. In this age group, the adjusted hazard ratio for consuming seven or more drinks per week was 2.26 (95% confidence interval: 1.19-4.32) compared with women consuming less than one drink per week. CONCLUSIONS These findings suggest that alcohol intake is a predictor for infertility problems among women in the later reproductive age group.