In animal studies pertaining to Vitamin E, varying amounts of fat have been used as essential constituents of the ration. Certain of these are known to have a specific influence on the rate of the oxidative changes in fats carrying the vitamins A and E. For example, wheat germ oil, a substance seemingly rich in Vitamin E., has been found to retard the oxidation of cod liver oil, as well as the destruction of Vitamins A and E; whereas lard hastens the destruction of these vitamins. Correlating these findings with the results of animal experiments, one is led to wonder if wheat germ oil is effective as an antisterility agent because of the presence of a specific vitamin, or because of its retarding influence on the oxidation of Vitamin A, a certain minimum of which is necessary for reproduction. It seemed possible that this might be determined by comparing the growth and reproductive behavior of animals receiving fat free rations, with animals receiving similar rations to which were added small amounts of wheat germ oil. We therefore have fed 3 groups of rats purified rations in which the Vitamins A and D were supplied by a cod liver oil concentrate (Oscodol). Vitamin B was furnished by starch free yeast. In one group the ration was supplemented with 3% of wheat oil; in another 12 gm. of lard was substituted for 27 gm. of cornstarch. All rations were made into a paste with distilled water, fresh mixtures being prepared approximately twice a week. TWO oscodol tablets, the equivalent of about 5% of the ration in cod liver oil, were added to every 488 calories of food. This, we have reason to believe, furnished a plethora of Vitamin A.