To identify strategies to prevent sexual problems in teenage girls, respondents in this study answered two open-ended questions: "What are strategies for teenage school girls to prevent unwanted coitus?" and "What are strategies for teenage girls to prevent pregnancy?" The respondents were 12,733 girls from an accessible population of 19,000, a multi-stage cluster sample from a population of 1,988,902 girls attending 4,684 schools in the seven largest cities and nine provinces in Korea. Data were collected by mail between October 2 and October 28, 2000. The response rate was 68.9%. The total number of responses for the first question was 10,345, and for the second, 9,624. Data were analyzed by content analysis. The results of this study are: 1. According to priority, frequent strategies to prevent unwanted coitus were, self assertiveness (35.7%), heterosexual interaction training (24.6%), sex education (21.2%), and innovations in the system of social culture (4.7%). The order of priority was the same whether the respondents had experienced coitus or not. 2. According to priority, frequent strategies to prevent pregnancy were, heterosexual interaction training (27.4%), sex education (26.2%), contraceptive use and induced abortion (21.4%), and innovations in the system of social culture (3.2%). The first priority for the respondents who had not experienced coitus was heterosexual interaction training (27.7%) but contraceptive use (35.5%) was the first priority for the group who had experienced coitus. In sex education, a focus on contraceptive use for teenage girls who have experienced coitus and on heterosexual interaction training for those who have not, would strengthen preventive strategies for these two sexual problems. Assertiveness training as part of sex education would further strengthen prevention strategies.