Background: Adolescence is associated with the transition from children to adulthood. Rapid physical changes and hormonal changes are triggers for adolescent health problems due to the emergence of sexual motivation that makes adolescents prone to diseases and reproductive health problems (kespro), teenage pregnancy with all its consequences, namely premarital sex, abortion, sexually transmitted diseases (STDs), HIV-AIDS and narcotics (Margaretha, 2012). Most people with HIV AIDS are at the age of 25-39 years, while someone exposed to the HIV virus will not cause symptoms within 5-10 years. Thus, the possibility of contracting HIV during adolescence. The highest risk factor for HIV is sexual intercourse. Meanwhile, sex education as an effort to prevent HIV AIDS in Indonesia is still considered taboo and has not received sufficient attention from all circles.
 Purpose: Knowing the Description of Youth Knowledge Level about HIV / AIDS in SMA N 1 Selemadeg
 Method: This research method uses descriptive research design. The sampling technique used in this study was purposive sampling technique with a total sample of 161 respondents. The analysis used in this research is univariate analysis which produces a frequency distribution.
 Results: This study shows that based on the level of knowledge of the respondents about HIV / AIDS, most of the respondents were less knowledgeable as many as 66 respondents (41%), enough as many as 52 respondents (32.3%), both 43 respondents (26.7%).
 Conclusion: The description of the level of knowledge of adolescents about HIV / AIDS in SMA N 1 Selemadeg showed that the level of adolescent knowledge about HIV / AIDS was lacking