In order to clarify the impersonated factors which may affect high school achievement, the following four studies were carried out by using three hundred high school students. The purpose of the study I was to compare the psychological traits of over, normal and underachievers (OA, NA, UA) on the basis of the following five tests: (1) Yatabe-Guilford personality test (YGPT),(2) Uchida-Kraepelin performance test (UKPT),(3) Creativity test,(4) Achievement motivation test (McClelland's), and (5) EIPC (The estimative inventory for the problem child). The difference between OA and UA was found to be statistically significant with respect to UKPT, and it was pointed out thatwillis important as a factor. The study II was that canonical and discriminant analysis were attempted with the same data of UKPT as used in the study I. As a result of it an unexpected clear separation among the three groups was obtained. This indicates that the subjective judgment of the profile in study I is correct as a whole, and that the application of these two analyseslto UKPT is very useful. The purpose of the study III was to examine to what degree the multiple regression analysis using UKPT and intelligence test results could account for the academic achievement variance. The result indicated that the largest correlation coefficient was 0.368 when the measures of UKPT were four and those of intelligence test three. Therefore, the explanation was not always satisfactory. If the predictor variables were used in this way, however, predictive power was generally higher for UKPT than for the intelligence test. In order to improve the accuracy of prediction, an study IV was designed as follows:Twelve raw scores of subtests in intelligence test, nine measures in UKPT, and twelve scale scores in YGPT were adopted separately or together as predictor variables; Nine achievement records at the end of school year were used as criterion variables, and then canonical correlation coefficients between both variables were calculated. The magnitudes of the coefficient correlats with a certain test were 0.542 with intelligence test, 0.448 with UKPY and 0.378 with YGPT. The coefficient based on over-all tests was 0.603. It was proved from this result that all subtest scores of intelligence test became the strongestfactor among the three tests, and that predictive power was highly improved in comparison with the use of IQ or T-scores alone. Considering these results, we may conclude that the factors by which high school achievement is effected, are strongest for intelligence, second for will, and weakest for emotion. Furthermore, it was. clear that the providing power (coeffifient of determinant) with these tests occupied thirty-six perce nt of all power.