BACKGROUD: It is not consistent on whether melatonin correlates with the adolescent idiopathic scoliosis(AIS) demonstrated by the domestic and foreign scholars.OBJECTIVE: To study the pathogenesis of AIS and its correlation with melatonin.DESIGN: A nonrandomized age-matched controlled study screened with two tests.SETTING: The Second Department of Orthopaedics, Haikou People' s Hospital.PARTICIPANTS: The experiment was completed in the Second Department of Orthopaedics, Haikou People' s Hospital. Totally 8 198 in-school students.from over 10 schools of towns in Haifu District, 4 423 males and 3 775 females, aged 7 to 16 years were surveyed.METHODS: Forty-two adolescents who have been diagnosed with AIS were selected and 50 healthy age-matched adolescents were selected as controls. Melatonin was assayed with the radioimmunology and the data were processed statistically.MAIN OUTCOME MEASURES: The levels of serum melatonin in the two groups.RESULTS: The serum melatonin of the preadolescents below 10 years old in AIS group, especially of females, was less than that of adolescents in the control group, with significant differencein statistics.CONCLUSION: The serum melatonin correlates with pathogenesis of AIS.