This study is designed to offer basic materials to supply adolescents with desirable personality and life guidance and to encourage them to ultimately form positive self-concept and to enhance mental health. According to this idea, the researcher came up with the following research problems to solve; First, what differences are there in adolescents' self-concept by sex and grade? Second, what differences are there in adolescents' mental health by sex and grade? Third, what correlation is there between adolescents' self-concept and mental health? The subjects were composed of a total of 335 middle school students located in Kangreung-si, Kangweon Province. The researcher depended upon 110-question test scale worked out by Kim Yong-rae(1995) aimed at measuring self-concept and 47-question simple mental examination test manufactured by Yi Hun-gu(1992) on the basis of System Check List(90 questions) developed by Derogatis, et al. The following are the findings of this study; First, the male subjects proved to be statistically higher than their counterparts in terms of gender differences in self-concept. The survey on the differences of self-concept by grade shows that the first graders were high in terms of the average of non-academic self-concept and the results of Scheffé test reveal that there was a significant difference in case of the third graders and the first graders. Second, the investigation on the difference in mental health by gender indicates that the boys proved to be a little lower but that there was no statistic significance and that the boys and that in terms of depression among the subordinate factors the boys were lower than the girls, or a little statistical significance. The survey on the differences in mental hygiene by grade shows that the first graders' level of mental hygiene was good in terms of all the subordinate factors including the whole mental health, followed by the second graders and the third graders in the right order. Scheffé test indicates that there was a little significant difference between the first graders and the third graders. Third, the investigation into the correlation between self-concept and mental health shows that the whole self-concept and the subordinate factors of self-concept were the most highly correlated with mental health. The survey shows that the correlation between non-academic self-concept and mental health was more significant than the correlation between academic self-concept and mental health. All in all, the present investigation has it that positive self-concept and sound mental health had more to do with non-academic factors than with academic factors. It follows that more serious efforts should be made to the personality education of youths than the cramming of knowledge in the field of pedagogy and that aggressive concern and guidance should be highlighted to determine what conflict students with lower self-concept and mental health have and to solve it so that they may grow into men and women with great personality after spending their middle school life with good mental health and confidence in school life, friendship and learning.