The vitamin A, carotene and xanthophyll contents of the yolks of eggs produced by 300 hens in groups fed on different diets during a 90 day period were determined colorimetri-cally. Storage of vit. A before laying begins and individual capacities of the hens may cause marked initial differences, but after some time the amt. of the 3 substances in the yolks depends chiefly on the ration. Dehydrated alfalfa, cod liver oil or dohyfral oil feeding brought hens which had previously been reduced to a state of vit. A exhaustion into a condition where they laid eggs with yolks 2 to 4 times as potent in vit. A as before. The highest values were found in eggs from hens fed on a diet containing both yellow maize and dehydrated alfalfa. Yellow maize alone (25% of the rations) produced yolks with a vit. A content of 150 I.U. per yolk; 7.5% alfalfa (140 [gamma] carotene per g.) 270 [gamma] per yolk. The vit. A potency is derived mainly from the vit. itself, although the chief dietary source of the vit. is carotene. Yolks with the highest vit. A content had a carotene content of only 40 [gamma], the poorest less than 10 [gamma]. The yellow color of the yolk is due chiefly to xanthophyll, of which much more is present than of carotene. Strongly colored eggs are generally also rich in vit. A and carotene, because the xanthophyll in them is derived in part from components of the diet which also contain considerable carotene. Green fodder plays a very important part in producing vit. A potency in eggs. The results agree well with those obtained by the biological method.