Alcohol consumption impairs neutrophil, macrophage, and T-cell functions, increasing the likelihood of infections. We examined the association between alcohol consumption and periodontitis, prospectively, among 39,461 male health professionals aged 40 to 75 years and free of periodontitis at the start of follow-up. Alcohol intake was assessed at baseline and updated every 4 years by a food-frequency questionnaire. Periodontal disease status was self-reported and validated against radiographs. Multivariate analysis was adjusted for age, smoking, diabetes, body-mass index, physical activity, time period, and caloric intake. During 406,160 person-years of follow-up, there were 2125 cases of periodontitis. Compared with non-drinkers, the relative risk (95% confidence interval) among men reporting usual alcohol intake of 0.1-4.9 g/day was 1.24 (1.09, 1.42); 5.0 to 14.9 g/day, 1.18 (1.04, 1.35); 15 to 29.9 g/day, 1.18 (1.01, 1.38); and > 30 g/day, 1.27 (1.08, 1.49). The results suggest that alcohol consumption is an independent modifiable risk factor for periodontitis.