OBJECTIVE: To identify the clinical characteristics and investigate function related aspects of Korean children with Rett syndrome. METHOD: A total of 26 patients diagnosed as Rett syndrome were clinically observed until the age of five or over. We surveyed past history, developmental history, and presence of typical clinical features of Rett syndrome. Furthermore, we investigated differences in clinical characteristics according to functional status and changes in clinical features related to growth. RESULTS: There were no problems related to gestational, perinatal or neonatal history. Only 12 patients had an ultimate head circumference of less than 3 percentile. Developmental regression was definite in all patients. At final assessment, only 14 patients were able to walk. Twenty patients had an epileptic history requiring medication. Sixteen patients with scoliosis showed progression during serial follow-up. The percentage of patients who were able to walk before 16 months was higher in the high function group than the low function group. The age of regression was 5.4 and 4.0 years in the high and low function group respectively, but the difference was not statistically significant. Scoliosis was more severe and seizure onset age was younger in the low function group. CONCLUSION: We investigated 26 clinical characteristics in Korean children with Rett syndrome. Their clinical features change according to age, and we believe such knowledge could be utilized in rehabilitation to minimize their disabilities.