ABSTRACT Objective: To apprehend the social representations elaborated by older people about HIV/AIDS and to understand how they relate to the prevention of HIV infection. Method: Descriptive and qualitative research based on the Theory of Social Representations with 42 older people assisted at primary care. Data were produced through in-depth interviews with a semi-structured instrument, processed in the IRaMuTeQ software, and analyzed by means of the descending hierarchical classification. Results: Five classes emerged: “HIV/AIDS: a problem of young people”; “Quality of life improvement for people living with HIV/AIDS”; “Vulnerability to HIV/AIDS among heterosexual women in a stable union”; “HIV/AIDS Information Network: process of creation and transformation of social representations” and “Prevention versus stigma”. Final considerations: The social representations that older people have about HIV/AIDS influence the adoption of preventive measures negatively because stigma is present and HIV/AIDS is attributed to young men, and to men who have sex with other men.