OBJECTIVE: The objectives of the present study were to investigate the annual detection rate of patients with Moyamoya disease (MMD) and to describe the prevalence and epidemiological features of the Moyamoya patients in Korea. MATERIALS AND METHODS: The authors analyzed the epidemiological data of Korean patients taken from the National Health Insurance Corporation in Korea among Moyamoya patients who were treated from 2004 until 2008. RESULTS: Based on 2004 data, 2,539 MMD patients were treated in Korea and the prevalence rate was 5.2 per 100,000 people. There were 2,987 in 2005, 3,429 in 2006, 4,051 in 2007, and 4,517 cases in 2008, and the prevalence rates per 100.000 people were 6.3, 7.0, 8.6, and 9.1, for those respective years. This represents an annual increase of 15% of new cases during this period. In 2008, 466 people were newly diagnosed with MMD, representing an incidence rate of 1 per 100,000 persons. The gender ratio was 1,547 men (34%) and 2,970 women (66%). Women had a higher incidence rate than men (1.94 times). There were two age peaks: teenagers and those in their forties. CONCLUSION: The present study shows that the number of Moyamoya patients in Korea is increasing. This increase could partly be explained by a recent increase in newly diagnosed cases, suggesting that a more careful consideration of the disease and better diagnostic techniques should be promoted among clinicians.