Knowledge on HIV/AIDS has accumulated after two decades of the epidemic; however, studies show the need for changes in teaching so as to transform future professionals' attitudes. In this scenario, the present study aimed at identifying the HIV/AIDS knowledge of students in the fifth year of a medicine undergraduate program. A positive self-evaluation concerning HIV/AIDS knowledge was found in association with undergraduate education as regards to biosafety for professional practice. Nevertheless, concerning sexual behavior, academic education did not have the same impact, since students reported previous knowledge, which was acquired from the media, secondary education and family and social relations, as determinant in their sexual practice. The results presented showed that teaching establishments must be responsible for critical awareness, which can develop prevention as the best form to control the disease. But this type of knowledge must make sense to students as future health care professionals, and particularly as citizens who are exposed to risks.