The main purpose of this study was to investigate the relationship between masturbatory knowledge and masturbatory attitudes among Taiwan adolescents. This study was based on a structured questionnaire survey that used the Adolescent Masturbatory Knowledge Inventory (AMKI) and the Adolescent Negative Attitude toward Masturbation Inventory (ANAMI). Subjects were recruited from the third grade of high school and vocational school students aged 17-18 living in Kaohsiung (southern Taiwan) using stratified and cluster sampling approaches. Seven hundred and eighty questionnaires were sent out, with a 96.8% response rate. A total of 95.3% of male subjects and 30.3% of female subjects reported having masturbation experience. Masturbatory knowledge was significantly related to the variables "school system", "frequency of viewing pornographic media", "status of being sexually active", and "conversation about sex with friends". Masturbatory attitudes were significantly associated with the same variables as well as with gender and masturbatory behavior. Masturbatory attitudes were positively correlated with masturbatory knowledge. The school system explained 15.4% of masturbatory knowledge variance. Masturbatory knowledge, masturbatory behavior, frequency of viewing pornographic media and status of being sexually active explained 39.5% of masturbatory attitude variance. In conclusion, adolescents in Taiwan hold positive attitudes toward masturbation and reported having insufficient knowledge regarding masturbation. Results can assist school staffs and parents to gain a deeper understanding of adolescents' knowledge about and attitudes toward masturbation.