Background: Despite the rollout of Medicare Part D, cost-related nonadherence (CRN) among older adults remains a problem. Objectives:: To examine the rate and correlates of self-reported CRN among a population of older persons with diabetes. Research Design:: Cross-sectional. Subjects: A total of 1264 Part D patients with diabetes, who entered the coverage gap in 2006. Measures: Initial administrative medication lists were verified in computer-assisted telephone interviews, in which participants brought their medication bottles to the phone. Medications were classified into cardiometabolic (diabetes, hypertension, cholesterol-lowering), symptom relief, and "other." Participants were asked if they had any CRN during 2006, and if so to which medication/s. We used the person-medication dyad as the unit of analysis, and tested a multivariate random effects logistic regression model to analyze the correlates of CRN. Results: Approximately 16% of participants reported CRN. CRN was more frequent for cholesterol-lowering medications (relative risk, 1.54; 95% confidence interval, 1.01-2.32) compared with medications taken for symptom relief. CRN was reported less frequently with increasing age above 75 years, compared with patients between 65 and 69. In addition, compared with those with incomes of ≥$40,000, CRN risk for those with incomes of <$25,000 was markedly higher (relative risk, 3.05; 95% confidence interval, 1.99-4.65). Conclusions: In summary, we found high rates of CRN among Medicare beneficiaries with diabetes, particularly those with lower incomes. We observed more frequent CRN for cholesterol-lowering medications as compared with medications for symptom relief. Efforts to ensure medication affordability for this population will be important in boosting adherence to key medications. © 2012 by Lippincott Williams & Wilkins.