Objectives : The objectives of this study were to estimate the continuity of care for all Koreans with diabetes and to identify factors affecting the continuity of care. Methods : We obtained National Health Insurance claims data for patients with diabetes who visited health-care providers during the year 2004. A total of 1,498,327 patients were included as study subjects. Most Frequent Provider Continuity (MFPC) and Modified, Modified Continuity Index (MMCI) were used as indexes of continuity of care. A multiple linear regression analysis was used to identify factors affecting continuity of care. Results : The average continuity of care in the entire population of 1,498,327 patients was $0.89{pm}0.17$ as calculated by MFPC and $0.92{pm}0.16$ by MMCI. In a multiple linear regression analysis, both MFPC and MMCI were lower for females than males, disabled than non-disabled, Medicaid beneficiaries than health insurance beneficiaries, patients with low monthly insurance contributions, patients in rural residential areas, and patients whose most frequently visited provider is the hospital. Conclusions : The continuity of care for patients with diabetes is high in Korea. However, women, the disabled and people of low socio-economic status have relatively low continuity of care. Therefore, our first priority is to promote a diabetes management program for these patients.