The HIV/AIDS epidemic in India is expanding rapidly. The present study is a pre-test-post-test evaluation of a school-based HIV/AIDS educational program. The pre-test was administered to 2,919 students regarding modes of transmission and prevention of HIV/AIDS. An education program was instituted for one half school day at ten secondary schools. Principals of two schools refused to participate. One month later, the post-test was administered to 2,400 students. Before the educational intervention only 50% of the students knew that HIV/AIDS is transmitted sexually, only 34% knew that there are no medicines that cure HIV/AIDS and 24% thought that HIV is transmitted by mosquito bites. After the intervention, 95% of the students knew that HIV/AIDS is transmitted sexually, 92% knew that there is no HIV/AIDS cure and 76% knew that HIV/AIDS is not transmitted by mosquitos. There was a substantial increase in correct knowledge about HIV/AIDS among students after our single educational program. This suggests that school-based educational programs for adolescents in India can succeed in providing basic information regarding HIV/AIDS.