Purpose: To evaluate the prevalence of refractive error and causes of visual impairment in school aged children, 2011-2012 school-year in Quy Nhon city, Binh Dinh province. Methods: Cross-sectional descriptive using proportional stratified random cluster sampling, 7.200 students were selected from 36 schools (clusters) representing 47.396 students of whole city, aged 7-18 year, representing 2 areas of residence (urban and suburban) and 3 grade degres. In all participants (6.809 students, 95.94 percent), uncorrected visual acuity and best corrected visual acuity were determined, and those with a visual acuity of 0.3 (20/40) or worse, underwent a cycloplegic refraction for evaluating prevalence of refractive errors and a complete ophthalmic examination to determine the causes of visual impairment. Results: The overal prevalence of refractive error was 27.35 percent, myopia 10.34 percent, hyperopia 0.04 percent, astigmatism 16.97 percent and anisometropia 1.80 percent. The prevalence of myopia was higher in students of 31h grade (21.21 percent) than those of 2nd grade (11.84 percent) and of 1S1 grade (3.32 percent). The prevalence of myopia increased according to grade (p 0.001). The prevalence of myopia was higher in females than in males and in urban than in suburban (p 0.001). In contrast, there were no significant statistically relation betwween the prevalence of hyperopia and sex, area of residence, grade. The prevalence of astigmatism increased according to grade (p 0.001) that was 14. 71 percent, 17. 79 percent and 20. 05 percent respectively. The prevalence a/astigmatism was higher infemals than in males and higher in urban than in suburban (p 0.001). There was a strong positive correlation between the prevalence of refractive error, myopia, astigmatism and age (R