This study was performed to provide preliminary data for the development of a useful instrument to measure the effect of sex education. The study was conducted with the voluntary participation of 155 college students enrolled in the course "Sexuality and Relationship" at Y university in Seoul. At the end of that course, they were asked to write freely about the change they had experienced on sexuality. All meaningful statements were elicited and classified into 7 categories; "Change of Knowledge", "Enlightenment", "Change of Attitude on Sexuality", "Buildup of Ability", "Buildup of. Identity", "Change of Emotion", "Change of Behavior:' There were significant changes in the areas of knowledge(28. 6%), enlightenment(27.4%), and attitudes(20.3%) about sexuality among these 7 categories. The Change of Knowledge category consists of 3 areas: "concretion of knowledge", "increase of information", and "correction of misunderstanding." In the category of Enlightenment, total 12 areas are included: "sex role", "erception of lack of knowledge", "importance of family", "life plan", "parent role", "value of life", "equality", "sexual autonomy", "importance of sexuality", "freedom of sexuality", "perception of sexual problem", and "meaning of love." The Attitude Change category consists of 8 areas. These are "being natural", "being progressive", "being sensitive", "being truthful", "being expressive", "being cautious", "being responsible", and "being confident". The category of Buildup of Ability includes 4 areas: "problem solving", "sex education", "relationship", and "communication". The category of Buildup of Identity includes "sexual identity", and "value of sexuality". The Emotional Change category includes 3 areas: "positive feeling", "negative feeling", and "breaking from negative feeling on sexuality". The Behavior Change category includes "sex-related behavioral change". In conclusion, up to now most researches on sex education effect measures only changes of knowledge, attitude, and behavior. But we believe the changes in "Enlightenment", "Buildup of Ability", "Buildup of Identity", "Change of Emotion", should be included in addition to knowledge, attitude, and behavior in the development of an instrument to measure the sex education effects. And the effect of sex education should measure the degree of learning of autonomy, enlightenment, and ability of behavior and so on rather than studying the simple changes in sexuality.enment", "Buildup of Ability", "Buildup of Identity", "Change of Emotion", should be included in addition to knowledge, attitude, and behavior in the development of an instrument to measure the sex education effects. And the effect of sex education should measure the degree of learning of autonomy, enlightenment, and ability of behavior and so on rather than studying the simple changes in sexuality.ng the simple changes in sexuality.