Background: Inadequate knowledge about HIV/AIDS, indulgence in risky health behavior leads the adolescents susceptible to this deadly disease. Objectives of the Study is to evaluate knowledge, attitude and perception, to know the correlation between knowledge, perception and attitude of students and to determine the association between the selected demographic variables with knowledge, perception and attitude score of students of Government schools towards HIV/AIDS. Material & Methods: This descriptive study was conducted among four senior secondary schools in Shimla city. A purposive sampling technique was used to select the schools and two classes from each school (11th -12th) were selected and 50 adolescents (age 14-19 yrs) from each class were included randomly. Information regarding their socio-demographic characteristics, knowledge, attitude and perception regarding HIV/AIDS were obtained using a self-administered, pre-tested, semi-structured questionnaire. Data was analyzed using Epi info v7 software using appropriate statistical tests. Results: In the present study most of the students (55.5% ) were in the age group of 17-19 years, maximum (60%) were male , 56.5% were in 10+ 2 class and 51.2% of the students having their source of information about HIV/AIDS were teachers. 31.5% having good knowledge, , 18.5% having good attitude and 15.8% having good perception about HIV/AIDS. A Correlation between attitude and knowledge & Perception of the students was found to be statistically significant Good knowledge about HIV/AIDS among students was significantly associated with 17- 19 years age group,10+2 class, joint family, higher educational level of father , higher educational level of mother and family having Monthly Income >10,000 (in rupees). Good attitude was significantly associated with higher educational level of mother and good perception was significantly associated with 10+2 class and family having Monthly Income >10,000 (in rupees). Conclusion:These f