This paper describes the process of building and validating the AIDS Prevention Questionnaire (CPS), a brief HIV risk assessment measure. An initial 64-items bank was filled out by 466 young people (192 men and 274 women), aged between 17 and 26 years (M = 20.62; SD = 2.15). The exploratory factor analysis revealed five components: Knowledge about HIV, Condom Attitudes, Intentions of Condom Use, Safe sexual behavior and Stigma and discrimination towards people living with HIV. This structure was confirmed by confirmatory factor analysis. The internal consistency for the different components ranged from .67 to .74. Moreover, CPS has a classification system that allows determining the level of risk. These results support the AIDS Prevention Questionnaire as a valid and reliable measure to detect earlier the risk for HIV infection and to design adjusted preventive interventions.