OBJECTIVE: To assess the effect of a specialist telemedicine intervention for improving diabetes care using the chronic care model (CCM). PARTICIPANTS AND METHODS: As part of the CCM, 97 primary care physicians at 6 primary care practices in Rochester, MN, referred 639 patients to an on-site diabetes educator between July 1, 2001, and December 31, 2003. On first referral, physicians were centrally randomized to receive a telemedicine intervention (specialty advice and evidence-based messages regarding medication management for cardiovascular risk) or no intervention, keeping outcome assessors and data analysts blinded to group assignment. After each subsequent clinical encounter, endocrinologists reviewed an abstract from the patient's electronic medical record and provided management recommendations and supporting evidence to intervention physicians via e-mail. Control physicians received e-mail with periodic generic information about cardiovascular risk reduction in diabetes. Outcome measures included diabetes care processes (diabetes test completion), outcomes (metabolic and cardiovascular risk factors, estimated coronary artery disease risk), and patient costs (payer perspective). RESULTS: During the intervention, 951 (70%) of the 1361 endocrinology reviews detected performance gaps and resulted in a message; primary care physicians reported using 49% of messages in patient care. With a mean of 21 months' follow-up, the intervention, compared with control, did not significantly enhance metabolic outcomes or reduce estimated risk of coronary artery disease (adjusted mean difference, -1%; 95% confidence interval, -19% to 17%). The intervention group incurred lower costs (P=.02) but not in diabetes-related costs. CONCLUSION: Specialty telemedicine did not significantly enhance the value of CCM in primary care. © 2008 Mayo Foundation for Medical Education and Research.