BACKGROUND: The purpose of this study is to analyze the scale of and trends associated with the cost-of-illness of thyroid disease in Korea at 2-year intervals during the last 10 years for which data are available. METHODS: Cost-of-illness was estimated in terms of direct and indirect costs. Direct costs include direct medical costs due to hospitalization, outpatient and pharmacy sectors, transportation, and care-giver costs. Indirect costs include future income loss due to premature death and loss of productivity as a result of absence from work. RESULTS: The cost-of-illness of thyroid disease in Korea was estimated at 224.2 billion won in 2002, 303.4 billion won in 2004, 400.3 billion won in 2006, 570.4 billion won in 2008, and 762.2 billion won in 2010. For example, the cost-of-illness of thyroid disease in 2010 was 3.4 times greater compared to 2002. The direct cost of the total cost-of-illness was 69.7%, which accounted for the highest proportion of costs. Cost-of-illness for individuals between the ages of 30 and 50 accounted for the greatest share of costs. CONCLUSION: The cost-of-illness of thyroid disease was relatively large in economically active age groups, and demonstrated a very rapid growth rate compared to other major diseases in Korea. Therefore, we suggest nationwide recognition of the importance of prevention and management of thyroid disease and prioritization of the management of thyroid disease among current and future health promotion policies in Korea.