The purpose of the study was to explore gender differences in knowledge and attitudes towards menstruation among Taiwanese adolescents. This study was a secondary data analysis of a cross-sectional comparison study conducted in Taiwan. A total of 287 female and 269 male students at a junior high school participated in the study. The results showed that almost all the students had heard about menstruation and most of them had received menstrual information at school. However, their knowledge about menstruation was not accurate. Moreover, the male students expressed more negative attitudes towards menstruation than the female students. Taboos were heard by most students and, although many female students doubted the reality of the taboos they had heard, they observed them anyway. The study calls for an evaluation of sex education and suggests more open discussions about menstruation among young people in those education sessions. In addition, school nurses and obstetrical/gynecological nurses should be involved more in adolescents' sexual education.