PURPOSE: Language disorders are characterized by inadequate acquisition of language comprehension or expression. Language disorder involve the exclusion of etiologic or explanatory factors, such as sttutering, delayed speech and phonological disorders. It is important to rule out etiologic factors because delayed speech is often associated with other organic disorders or causes of secondary problems. There is no statistic analysis of the causes of language disorders in Korea. So, we analysed the causes of language disorders. METHODS: From March, 2001 to August, 2003, we examined 113 children with language disorders who had developmental and language tests in the language therapy center in Chungnam National University Hospital. RESULTS: In 113 children with language disorders, 77% are male and 23% are female. Average age is 51.3 months. The causes of language disorders are mental retardation (42.4%), tongue-tie(12.3%), sttutering(10.6%), developmental language disorders(9.7%), articulation disorders(9.7%), autism(5.3%), cleft lips or cleft palates(4.4%), hearing disorders (2.6%), lack of teaching(2.6%). CONCLUSION: These data demonstrate that mental retardation is the most common cause of language disorders. It is important to pediatricians that early diagnosis and early therapy can prevent developmental or learning disabilities of children with language disorders.