The refraction of 12 street cats' eyes and of 11 caged cats was measured by retinoscopy, and the anteroposterior (axial) length of the eyeball was measured by ultrasound. While 87.5 per cent of eyes in street cats were found hypermetropic (average + 1.14 D), among cats caged for periods of 8.5-14.0 months under conditions of near vision. 68.2 per cent were myopic (average, -0.62 D). The anteroposterior length of the eyeball was practically equal in both groups (20.43 mm): it was also practically equal for myopic and hypermetropic eyes. The site of the refractive changes is discussed.