The purpose of this cross section study was to describe the amount of students’ knowledge in Hamadan University of Medical Sciences (HUMS) about AIDS (Acquires Immunodeficiency Syndrome). 1272 students participate in this study as well as completed questionnaire. The pilot study perceived with 300 subjects to evaluate validity and reliability of the AIDS knowledge questionnaire before applying the study. Data were analyzed using EPI6 statistical software. It was found that 67% of the students had a good level of knowledge, but the other 32.2% had low level of knowledge about AIDS. In addition, where was correlation between level of the knowledge and their major study and age.