The authors aimed to determine the prevalence of amblyopia, its relation with refractive errors and its determinants. The target population was all children aged seven years in Iran. There were 3675 of 4157 children who participated (88.4%) with final analysis on 3547 children with full data. Sixty-three had amblyopia (1.88%: 1.91% male and 1.85% female). Of that 60.3% had unilateral amblyopia; 73.9% had corrected visual acuity better than 20/40 and 5.7% with visual acuity <20.80; 51.3% had strabismic amblyopia, 27% anisometropic, 9.5% isotropic, 11.1% strabismic plus anisometropic, and 1% with stimulus deprivation amblyopia due to cataract. Amblyopic eyes were more hyperopic with a higher mean cylinder error. The authors conclude that attention should be paid to hyperopia and astigmatic refractive errors and to treatment of strabismus cases.