Eight white rats, stunted for 85 days by being fed on a standard diet with gliadin substituted for casein, took less time, made fewer errors, and traversed a shorter distance in relearning a maze than did 5 control rats which had grown normally and which were each slightly over twice the weight of the stunted animals. On realimentation, bringing the experimental rats to the same weight level as the controls, the differences in learning the maze disappeared. Femalc rats were given 30 trials on the maze; on the basis of their records they were divided into 3 groups of 18 each. One group was fed normally and grew normally; the 2nd was stunted by gliadin feeding (qualitative stunting); and the 3rd was stunted by low calorie feeding (quantitative stunting). After 28 days the 3 groups were given 18 trials in the original maze, 12 trials in a different maze, and 12 trials in the original maze, respectively. Both the qualitatively and the quantitatively stunted rats were superior in time reaction, both in relearning the old maze and in learning a new maze, to rats which grew at normal rates. The gliadin-stunted rats made fewer errors in relearning the old maze and the low-calorie rats made more errors both in relearning the old maze and in learning a new one than did the normal rats. Realimentation for 28 days brought the stunted animals near the normal animals both with respect to weight and maze-reacting ability.