Objectives: In order to develop a peer counseling program as a new strategy for youth-to-youth sex education, we examined whether the program modified cognition and behaviors of high school students regarding sexuality.###Methods: We administered a questionnaire about sexuality to high school students who participated in a peer counseling program under the auspices of the health centre from December 2003 to July 2004. The questionnaire contained Questions about sexually transmitted diseases, contraception, decision-making related to sexual behaviors, self-efficacy and self-esteem. This peer counseling program provided information about sexuality and negotiation skills in face of sexual pressures, was provided for hig-h school students by university students who had finished the peer counselor course using an empowerment-evaluation approach. The data were collected before and three months after the peer counseling program.###Results: 125 high school students were enrolled the peer coungeling program. The data from all students were collected before the peer counseling program. Follow-up data from 86 high school students were collected three months later. We were able to analyze 77 paired data on the pre-to post-intervention questionnaire.### 94.1% of the high school students had a favorable impression of the peer counseling program. They learned communication skills, and they reported an improved ability to form good human relations after the program. In addition, they reported an increase in knowledge and recognition about their sexuality. Scores of self-efficacy and self-esteem were higher after the program compared with scores before the program. As a result, it was suggested that their decision-making about safer sexual behaviors was improved.###Conclusion: Peer counseling, which is a new strategy of youth-to-youth sex education, was effective###in providing information and empowerment about sexuality for high school students.