Purpose:To describe strabismus prevalence and associated factors in a representative sample of 6-year-old Australian children.Design:Population-based cross-sectional study.Participants:One thousand seven hundred thirty-nine predominantly 6-year-old children resident in Sydney examined in 2003 and 2004.Methods:Cover testing was performed at near and distance fixation,and with spectacles if worn.Logarithm of the minimum angle of resolution visual acuity was measured in both eyes before and after pinhole correction,after correcting any cylindrical refraction>0.50 diopters and with spectacles,if worn.Cycloplegic autorefraction(cyclopentolate) and detailed dilated fundus examination were performed.Each child’s medical and perinatal histories were sought in a detailed parental questionnaire.Main Outcome Measures:Strabismus was de-fined as any heterotropia at near or distance fixation,or both,on cover testing.Microstrabismus was defined as a deviation of fewer than 10 prism diopters.Results:Strabismus was diagnosed in 48 children(2.8% of the population) ,5 of whom had previously undergone surgical correction;26 children(54%) had esotropia,14(29%) had exotropia,7(15%) had microstrabismus,and 1 child had VIth cranial nerve palsy.Pre-maturity was associated with a 5-fold increase in the risk of esotropia(odds ratio,5.0;95% confidence interval,1.8-14.1) .Visual impairment(with presenting correction) was signifi-cantly more common in children with(22.9%) than without(1.3%) strabismus(P< 0.0001) .The presence of strabismus was significantly associated with hyperopia,astigmatism,anisometropia,and amblyopia(P < 0.0001) .Conclusions:This report documents the prevalence of strabismus and its relation to other ocular signs and visual impairment in a representative sample of Australian school children.Presence of strabismus was significantly associated with prematurity. Purpose: To describe strabismus and associated factors in a representative sample of 6-year-old Australian children. Design: Population-based cross-sectional study. Participants: One thousand seven hundred thirty-nine predominantly 6-year-old children resident in Sydney examined in 2003 and 2004. Methods: Cover testing was performed at near and distance fixation, and with spectacles if worn. Logarithm of the minimum angle of resolution visual acuity was measured in both eyes before and after pinhole correction, after correcting any cylindrical refraction > 0.50 diopters and with spectacles, if worn. Cyclooplegic autorefraction (cyclopentolate) and detailed dilated fundus examination were performed. Every child’s medical and perinatal histories were sought in a detailed parental questionnaire. Main Outcome Measures: Strabismus was de-fined as any heterotropia at near or distance fixation, or both, on cover testing. Microstobismus was defined as a deviation of fewer than 10 prism diopters. Results: S had children (2.8% of the population), 5 of whom had previously undergone surgical correction; 26 children (54%) had esotropia, 14 (29%) had exotropia, 7 (15%) had microstrabismus, and 1 child had VIth cranial nerve palsy. Pre-maturity was associated with a 5-fold increase in the risk of esotropia (odds ratio, 5.0; 95% confidence interval, 1.8-14.1) .Visual impairment (with presenting correction) was signifi-cantly The presence of strabismus was significantly associated with hyperopia, astigmatism, anisometropia, and amblyopia (P <0.0001). Conclusions: This report documents the most common in children with (22.9% prevalence of strabismus and its relation to other ocular signs and visual impairment in a representative sample of Australian school children. Presence of strabismus was significantly associated with prematurity.