A study of the effects of dietary constituents upon the activity of synthetic folic acid in chick nutrition showed that no definite requirement for this compound can be established since the response to a given amt. of folic acid depends upon the type of ration used. Folid acid produced the least response with high-fat diets or diets containing glucose, sucrose, or starch as the sole carbohydrate, and the best response with diets containing high protein, low fat, or corn-meal and dextrin as the carbohydrates. Hb responses were better on diets containing dextrin or corn-meal than on diets containing other carbohydrates. Feather development could not be correlated with either the amt. of folic acid in the diet or the rate of growth of the chicks when the dietary levels of folic acid were low. Whole liver substance added to a diet containing sucrose as the carbohydrate gave an increased growth response not attributable to its folic acid content.