Seven naturally strabismic monkeys (Macaca nemestrina) was identified. Five of these monkeys were examined by ophthalmologists. No ophthalmoscopically obvious cause for the squint was found in any case. Of those five animals, two were tested behaviorally on visual responsiveness and visual acuity. The acuity of both eyes of both monkeys was somewhat poorer than normal. In addition, an amblyopia of 0.8 octaves was found for one monkey and 0.6 octaves for the others. The existence of naturally strabismic monkeys supports the utility of the macaque as an animal model for studying strabismus and amblyopia.