Two types (A and B) of standardized tests of ability in national language were prepared composed of five subtests in vocabulary, sentence reading, paragraph reading, language usage and information in literature. As the first step in the standardization, tests were administered with samples of one public highschool from each of the seven areas of the Metropolitan Prefecture of Tokyo. The subjects amounted separately to 1,484 for the A type test and 1,478 for the B type test. Statistical analysis of the results showed a very high degree of reliability and validity. The reliability as calculated with 100 9th grade students by the use of split-half method was 0.97 as corrected by the Speareman-Brown formula. The correlation between the test result and the scholastic score in national language ranged from 0.70 to 0.88. It was also proved that A and B type tests were approximately equivalent as planned beforehead. From these findings it is concluded that the present test could very well be used in the diagnosis and evaluation of the ability of the highschool students in national language. It has also been found by the sampling method that there are marked differences in the abilities from area to area but that there is hardly any difference between boy students and girl students. The Norm will be worked out with the indication of the size of deviation from the mean score (T score). These findings as the first step, a nation-wide study will be conducted for the standardization of the test of ability in the national language.