OBJECTIVE: To examine medical and mental health care expenditures for large numbers of individuals with diabetes enrolled in employment-sponsored insurance plans. RESEARCH DESIGN AND METHODS: Health insurance billing data for approximately 1.3 million individuals enrolled in health insurance plans sponsored by 862 large self-insured employers nationwide were used to examine employer expenditures and consumer out-of-pocket payments for 20,937 people identified with diabetes. These expenditures were compared with expenditures for individuals with other chronic illnesses. Main outcome measures were covered charges, insurance plan reimbursements, and estimated consumer out-of-pocket payments for both medical and mental health services. RESULTS: A total of 1.7% of enrollees were identified as having diabetes and approximately 11% of those used at least one mental health service during 1996. Health care expenditures were three times higher for those with diabetes compared with all health care consumers in these insurance plans, but when compared with individuals with other chronic illnesses such as heart disease, HIV/AIDS, cancer, and asthma, those with diabetes were not more expensive for employers' insurance plans. Diabetes accounts for 6.5% of total health plan expenditures. CONCLUSIONS: Diabetes is not more expensive for either consumers or their employer-sponsored insurance plans than other chronic illnesses.