The purpose of this study was to identify characteristics related to self assertiveness in teenage girls, and to identify the relationship between the self assertiveness and sexual experiences in teenage girls in Korea. The subjects for this study were 12,733 girls from an accessible population of 19,000 girls who were a multi-stage cluster sample from a population of 1,988,902 girls attending to 4,684 schools in the seven large cities and nine provinces of Korea. The response rate was 68.9%. Data were collected by mail from October 2 to October 28, 2000. A structured questionnaire of 125 items which included measurement of general characteristics, sexual experiences, and self-assertiveness was used. The sexual experiences were defined as dating, holding hands, putting arms on the shoulders, light kissing, French kissing, touching breasts, touching genitalia, and coitus. The self assertiveness measurement was developed by S. B. Chang et al.(2000) and has a Cronbach's alpha of .6031. Data was analyzed with SPSS 10.0 Program using descriptive statistics, reliability, and t-test. The results of this study are as follows;