This cross-sectional study analyzed social vulnerability, individual, and programmatic factors associated with low knowledge on HIV/AIDS among men who have sex with men (MSM). Respondent Driven Sampling (RDS) was used in 10 Brazilian cities. Knowledge scores on HIV/AIDS were estimated by Item Response Theory and categorized in three levels: high, medium, and low knowledge. Ordinal logistic regression was used for the analysis. Of the 3,746 MSM, 36.6%, 37.4%, and 26% showed high, medium, and low knowledge, respectively. The following were associated with low knowledge in the final model: schooling ≤ 8 years, non-white skin color, economic classes C and D-E, age < 25 years, having only one sex partner, and no previous HIV test. It is essential to improve knowledge on HIV/AIDS among young MSM with low socioeconomic status. Interventions focused on programmatic vulnerability factors can help reduce individual and social risk.
HIV; Risk Groups; Male Homosexuality; Health Knowledge, Attitudes, Practice; Health Vulnerability