We tested the validity of vision screening in schools in 7 regions of Oman in 2003. Two researchers tested 1719 randomly selected students in 4 school grades using the Snellen E acuity test. Trained school nurses had previously screened 182 233 students. The visual status recorded in the 2 screenings was compared. Sensitivity of screening by nurses was 68.34% (95% CI: 67.30-69.38) and specificity 99.23% (95% CI: 99.19-99.27). The positive predictive value was 85.42% (95% CI: 84.63-86.21) and negative predictive value was 97.93% (95% CI: 97.87-98.00). The sensitivity of the vision test was significantly higher in females, older students and in North Sharqiya region. In general, the vision screening of school students in Oman has satisfactory validity. Periodic training of nurses and supervision of the screening procedures could improve its sensitivity. Underlying causes of the high numbers of false negative cases should be further investigated.