1. A study was carried out on 973 school children to find out any relationship between vitamin B-complex deficiency signs and defective vision, and the effect of supplementation of B-complex vitamins on visual acuity. 2. The results of the study showed a significant association between presence of clinical signs of vitamin B-complex deficiency and defective vision. 3. Supplementation with vitamin B-complex was found to have a beneficial effect in improving the visual-acuity status of defective children and in preventing visual defects from developing. 4. It is concluded, therefore, that from the present study it appears that the relationship between vitamin B-complex deficiency and visual defects could be one of 'cause and effect'.