This research report examines prevalence and spending on diabetes for fee-for-service (FFS) beneficiaries of the Medicare program, the health insurance program that covers the majority of adults age 65 and above in the U.S. To date, most studies of spending on diabetes care in the U.S. have relied on self-reported survey data and estimates of utilization and spending, but do not represent actual spending identified through administrative claims. This report is based on newly available administrative claims data from the Centers for Medicare & Medicaid Services 2010 Chronic Conditions Public Use File. Diabetes was prevalent among approximately 1/4 of Medicare FFS beneficiaries in 2010. Prevalence increased with age initially for the aged population, but dropped for beneficiaries > 85. Only about 1/4 of diabetic beneficiaries had diabetes without a comorbidity. Beneficiaries with diabetes had 2.8 chronic conditions (including diabetes) with average Medicare Part A and Part B spending of $5,741 and $5,991, and drug costs of $3,119, respectively. Spending increased with age for beneficiaries >65. Findings of these analyses consider diabetes in the context of chronic comorbidities and contribute to understand claims-based prevalence and spending for older adults with diabetes in the Medicare FFS population.