A selective review of the effects of visual deprivation on acuity in animals has been presented along with data on the effects of visual deprivation on monocular acuities in children. A comparison of the visually deprived children and animals indicated (1) that no one deprivation state is a satisfactory model of the effects of visual deprivation but (2) that comparable deprivation states have similar effects on visual acuity across species (at least in cat, monkey, and human). Possible mechanisms involved in the development of amblyopia were presented: (1) binocular competition, (2) form deprivation resulting from retinal defocus, and (3) abnormal oculomotor proprioception. The presence of binocular amblyopia suggests that binocular competition is not a necessary condition for the development of amblyopia. The effects of patching therapy and treatment of human monocular deprivation or visual acuity were found to be consistent with their appropriate animal models. While animal models have great potential for elucidating the mechanisms of amblyopia, the limitations of any one deprivation model are clear. The development of visual assessment technique for infants and young children seems essential for therapy of the effects of visual deprivation, especially monocular deprivation.