The purpose of this survey, in which 2754 students from 35 middle schools from Taegu city participated, was to identify the degree and the relationship of sexual knowledge, sexual attitude and need for sex education. This information will provide useful data, and promote a more systematic, desirable and practical sex education. The data was collected from September 1 to November 8, 1997. Data was analyzed using the statistical computer package, SPSS to manipulate the data along with percentage, mean, $X^2$-test. t-test, F-test and Pearson correlation coefficient. The results from this study were summarized as follows: 1. The mean score of sex related knowledge showed significant differences between boys and girls in general knowledge(boys: 10.85 girls: 11.71, p=0.000), in the area of physical development(boys : 5.29 girls: 5.72, p=0.000), pregnancy & physiology (boys: 3.23 girls: 3.57, p=0.000) and venereal disease (boys: 2.33 girls: 2.42, p=0.000). 2. The mean score of sex related attitudes showed a significant differences between boys and girls on the whole(boys : 57.68 girls: 58.92, p=0.000), in the area of psychological differences of the other sex (boy: 26.13, girls: 28.08, p=0.000), and sexual delinquency and its prevention(boy: 14.28, girls: 13.68, p=0.000). However, in the area of other sex friendships (boy: 17.28, girls: 17.16, p=0.274). There were no significant differences between boys and girls. 3. Those who had a higher sex related knowledge score showed more positive attitudes towards sex, but was of no statistical significance(r= 0.312, p=0.000). 4. The majority of subjects wanted to learn about friendship with the other sex(40.1%), about physical and psychological differences in adolescence(24.0%), about prevention of sexual violence(15.0%), about pregnancy and delivery (7.5%), about venereal disease and medical cures(7.3%), about contraception methods (4.3%), as well as other aspects of sexual knowledge (1.8%), 5. The mean score of sex related knowledge generally was higher when one paid a lot of attention to health (F= 3. 148, p=0.014), when one's father was alive(t=3.930, p=0.000), and when one's mother was alive(t=2.807, p=0.005), Hobby activities also showed a significant difference(F=9.092, p=0.000). The mean score of sex related knowledge generally according higher when one had sex education(F=9.470, p=0.000), when one obtained sexual knowledges from a teacher (F = 5. 742, p=0.000), and when one had middle grade problems with sex(F=13.58 4, p=0.000). 6. The mean score of sex related attitudes generally showed significant differences when re ligion(F=2.691, p=0.03), hobbies (F= 3.499, p= 0.002) were considered. Those who had a father also had higher scores(t=2.538, p= 0.011). The mean score of sex related attitudes generally with respect to a subject's sex was higher when one had sex education(t=5.338, p= 0.000), when one had high grade problems with sex(F=6.023, p=0.002), and when one had the experience of friendship with the other sex(t= 8.106, p=0.000), The following suggestions are based on the above results, 1. Systematic sex education must be performed in middle schools in order to establish responsible attitudes toward sex, 2. Sexual knowledge, attitude, and general sex education classes must be performed seperately for early, middle, and late adolescents, In other words sex education programs are needed for each adolescent development stage.