The number of known disease-causing mutations has increased dramatically. However, there have been few organized mutation databases developed that are available to the public or notfor-profit entities. Thus, clinicians and diagnostic laboratories had to spend time searching many publications and databases to determine whether a mutation has been previously reported. To assist in genetic diagnoses, the systematic collection and curation of mutations is necessary. The Korean Mutation Database (KMD, http://kmd.cdc.go.kr) is a country-specific database of human gene mutations that was established in September, 2009. The KMD is a database consolidating mutations of genes related to diseases in Korea; it now contains more than 1,600 mutations from 245 genes. We collected mutation data from diagnostic laboratories and published journals over recent decades in Korea. KMD has been open to the public for searches and registration of mutation data without charge. Our aim is to provide organized information for clinicians and researchers who are interested in genetic diseases. It will be useful not only for researchers in Korea but also for those in countries with similar ethnic backgrounds. Ultimately, KMD will be an essential base to improve researches in genetic diseases, developments of diagnostics, and therapeutic optimization.