OBJECTIVE: To examine sex-specific associations between living alone and incident Type 2 diabetes mellitus in a representative population sample in Germany. METHODS: The study was based on 4424 men and 4380 women (aged 35-74 years) who participated in one of the three Monitoring trends and determinants on cardiovascular diseases Augsburg surveys between 1984 and 1995 and who were free of diabetes at baseline. Sex-specific hazard ratios (HRs) were estimated from Cox proportional hazard models. RESULTS: A total of 402 cases of incident Type 2 diabetes among men and 271 among women were registered during the mean follow-up period of 10.9 years. Living alone was significantly associated with incident Type 2 diabetes in men but not in women. After adjustment for age, survey, parental history of diabetes, hypertension, dyslipidemia, smoking, physical activity, alcohol intake, and body mass index, the risk of developing diabetes for those who lived alone at baseline compared with those who did not live alone was 1.69 (95% confidence interval (CI), 1.19-2.37) in men and 0.85 (95% CI, 0.57-1.24) in women; the p value for the sex interaction was .006 in this model. Inclusion of education and depressed mood in the models in addition to other risk factors had no impact on the observed HRs in women and even increased the risk in men (women: HR, 0.83; 95% CI, 0.52-1.32; men: HR, 1.89; 95% CI, 1.33-2.70). CONCLUSIONS: Living alone is an independent predictor of Type 2 diabetes in men but not in women from the general population.