That the constancy of the intelligence quotient has attracted much attention is shown by the great amount of research that has been done in order to verify the theory of constancy. Much of the literature concerning the problem has been concisely summarized by Foran (36, 37), Burks ( 16), and Baldwin (60). They have considered many of the studies in which the Stanford Revision of the Binet-Simon Tests was used; therefore, there seems to be a need for a review of investigations dealing with the constancy of the I.Q. derived from revisions of the Binet-Simon Tests other than the Stanford-Binet and group tests. Furthermore, various researches on the influence of training, environment, and physical condition on. the I.Q. have been made.