Background/Aims: Juvenile myopia is a serious problem in China, the prevalence of which stays at a high level and shows an upward trend. The target of this study was to explore the factors associated with myopia in Chinese children. Methods: A cross-sectional analysis in a random sample survey was conducted in Beijing in 2008. The data collected from 15,316 Chinese school students aged 6 to 18 years, randomly selected from 19 schools were evaluated, including noncycloplegic refraction and possible genetic, environmental and behavioral factors, to explore the key risk factors for myopia. Univariate and multiple logistic regression analyses were performed to compare the OR values, and receiver operator characteristic (ROC) curves were generated to compare the differences among the areas under the ROC curves using the method of multiple comparison with the best. Results: Myopia was associated with shorter sleep times versus longer sleep times (adjusted OR = 3.37; 95%CI 3.07-3.70), and the multivariate OR for two compared with no parents with myopic was 2.83 (95%CI 2.47-3.24) and 1.95 (95%CI 1.69-2.24) for reading or writing distances less than33 cmcompared to distances greater than33 cm. Controlling for other factors, children that slept for shorter periods of time had significantly more myopic refractions (?1.69D vs ?1.29D for children with longer sleeping time per day). Analysis of the areas under the ROC curves showed five variables with predictable values better than chance: age, sleeping time, reading or writing

distance, hours of studying, and parental myopia. Conclusion: It was not surprising, as proved by other studies, that parental myopia, reading or writing distances, time spent on studying or other activities by using eyes were dominant risk factors associated with juvenile myopia. Our findings indicated that hours of sleeping were also closely related to juvenile myopia, in which the underlying mechanism should be explored in the future study.