T his study evaluated the specialization status of Korean hospitals by applying index measures that were developed to determine how hospitals are specialized. In addition, multivariate regression analysis was applied to assess how the measures responded to the internal and external factors of hospitals. N ational Health Insurance claims for 2004 were used to calculate the information theory index, internal Herfindahl index, number of distinct diagnosis-related groups (DRGs) treated, and percent of the five most common DRGs. Data from the Ministry of Health and Welfare and Korean Hospital Association were used to determine the size, ownership, teaching status, organization type, and location of the hospitals. T he four indexes analyzed showed that there were significant differences in the specialization status of providers, depending on the provider size, organization type, and location. Hospitals that were smaller and located in metropolitan areas tended to provide specialized services; this is considered to constitute a competitive strategy for hospitals. It is expected that specialized hospitals will increase given the current market structure. Therefore, policy makers will need an index for measuring how hospital services are specialized. Information from such an index could provide a picture of how hospital services are mixed and change over time.