OBJECTIVE: To examine the association between antidepressant use, diagnosed depression, and new onset diabetes among elderly Medicare beneficiaries. MATERIALS AND METHODS: Longitudinal data from merged survey and claims from the nationally representative Medicare Current Beneficiary Survey(MCBS) from 1999-2005 were used. Diabetes incidence was extracted from claims and survey data over a 3-year period. Depression and antidepressant use data were obtained over time. Multivariable logistic regressions were used to examine association between antidepressant use, depression, and new onset diabetes, adjusted for demographic, socioeconomic, and lifestyle risk factors. Analyses accounted for complex design of MCBS. RESULTS: Incident diabetes rate was 4.8% for those "without depression and without antidepressants" and 9.5% for those with any antidepressant use in all 3-years and diagnosed depression. Compared to Medicare beneficiaries who did not report any antidepressant use, beneficiaries reporting antidepressant use in all 3-years were 50% more likely to have new onset diabetes. However, when diagnosed depression was entered in the model, we did not observe a statistically significant association between long-term antidepressant use and new onset diabetes. Medicare beneficiaries with any depression were twice as likely as those without depression to develop diabetes(AOR = 2.04, [1.51, 2.75). CONCLUSION: Depression could independently increase risk of developing diabetes, while there is no evidence of association between antidepressants and new onset diabetes. If replicated, these results have significant clinical implications. THE SIGNIFICANT FINDING OF THE STUDY: We found increased diabetes risk among Medicare beneficiaries with depression. THIS STUDY ADDS: Long-term use of antidepressants in the absence of depression increases risk of diabetes.