Based on data from the Semarang District Health Office in 2016, out of 19 sub-districts in Semarang Regency, the number of HIV / AIDS cases was high in 13 cases of Bergas Subdistrict, 22 cases of HIV / AIDS were found in October, 22 out of which 22 cases among them occur by adolescents in the 15-20 year age group included in the middle and advanced teen age groups.The purpose of this study was to find out the correlation of knowledge, perceptions and attitudes withHIV prevention behavior in adolescent . This research was conducted at Bergas 1 Public High School. This type of research is quantitative, with correlation research design. The sampling technique with Proportionate Stratified Random Sampling was done by simple random sampling with the number of respondents 87. The research instruments werequestionnaires.The results showed that the majority of the sexes of the respondents were female 55 (68.2%), the respondent's residence in the parent's house 68 (78.2%), sufficient knowledge of adolescents 37 (42.5%), perceptions of adolescents in HIV prevention / AIDS positive 54 (62.1%), adolescent attitudes in positive HIV / AIDS prevention 54 (62.1%), the behavior of HIV / AIDS prevention in adolescents was good 52 (59.8%). The Chi-Square results have a correlation of knowledge, perceptions and attitudes with HIV / AIDS prevention behavior in adolescents.From the results of this study, it is expected that adolescents want to participate in HIV / AIDS dissemination activities so that the knowledge of adolescents on HIV / AIDS prevention increases and is able to prevent HIV / AIDS. For health workers when conducting HIV / AIDS outreach should not coincide with other outreach so that the material presented focuses on HIV / AIDS prevention and the frequency of socialization is increased to 3 times in 1 year.