Résumé
<p><b>OBJECTIVE</b>To study the relationship between contraceptive use behaviors and related knowledge and cognition among vocational high school students.</p><p><b>METHODS</b>A computer-administrated anonymous cross-sectional survey was conducted among grade one students from three vocational high schools in a district of Shanghai. Based on Health Belief Model, four cognition indexes including perceived benefits, barriers, sex behavior related risks and self-efficacy were applied.</p><p><b>RESULTS</b>Among 1612 respondents, the students who had sexual experience accounted for 7.01% (113/1612). At first sex, 56.64% (64/113) of respondents reported contraceptives use; and the methods most reported were condom (58.70%, 27/46) and oral contraceptive (27.78%, 5/18) respectively for male and female. Most reasons for non-use were feeling shy to buy it (26.53%, 13/49) and the opposite sex's unwillingness to use (18.37%, 9/49). Among those who had experienced sex, 68.35% (54/79) and 68.42% (52/76) of respondents thought withdrawal and rhythm were effective methods. Only 23.26% (10/43) of subjects who had ever used condom could gain the full score of knowledge on how to use condom. A few respondents (22.86%, 24/105) who had sex experience knew that "If a person is infected with STD, he/she may not have noticeable symptoms". And 40.63% (26/64) of respondents who had not use contraceptive at first sex considered that "Infrequent intercourse cannot cause a girl pregnant even she has experienced her menstruation". The level of perceived risks was lowest among four cognition indexes. Contraceptive related knowledge and cognition may contribute to respondents' contraceptive use behaviors at first sex, and only related cognition contribute to contraceptive use behaviors at recent sex.</p><p><b>CONCLUSION</b>It should be urgent to improve contraception knowledge and cognition among vocational high school students and provide youth-friendly contraceptive services.</p>