The observation that galactose is unique as an etiologic factor in the production of experimental cataract in rats was first reported by Mitchell1and later confirmed by Yudkin2and Day.3The earlier work with lactose and other sugars4led to the realization that it was probably the galactose fraction of the lactose molecule which caused the injury. Galactose has supplanted lactose for the production of most of the experimental cataracts in the laboratory of the Massachusetts Agricultural Experiment Station because of the more rapid and consistent results obtained. Whichever sugar is used, however, it is logical to speak of galactose cataract in contrast to the vitamin G deficiency cataract. Both may well be designated as nutritional cataracts. The fact that the rat is susceptible to lenticular changes as a result of vitamin G deficiency or of intolerance for galactose makes it a valuable experimental animal