Objective: Health behavior theorists have proposed that cognitive variables (e.g., intentions to change, self-efficacy) drive individual health behaviors, and most HIV/AIDS prevention interventions are grounded in this notion. However, some scholars have suggested that marginalized groups experience structural barriers to enacting their healthy intentions, and thus, cognitive variables might be a poorer predictor of health behaviors in these populations. The purpose of the present study was to test the possibility that intentions are a poorer predictor of behavior among younger, lower SES, and ethnic minority individuals. Method: Using longitudinal data from a sample of men who have sex with men (N = 487), we examined whether baseline behavioral intentions to obtain an HIV test differed by socioeconomic status (SES), age, and race/ethnicity and whether the prospective association between intentions to test and subsequent testing differed by these sociodemographic variables. Results: Lower-status individuals expressed equal or greater intentions to obtain an HIV test at baseline. However, intentions to obtain an HIV test did not predict subsequent testing behavior among low-SES men and younger men. Race/ethnicity did not moderate the intentions-behavior relation. Conclusions: Although lower-status individuals express equal or greater intentions to obtain HIV testing, they appear to be less likely to act on these intentions. HIV prevention strategies that target cognitive variables, such as intentions, must recognize that they may be less reliable predictors of health behavior among vulnerable populations. Future research and interventions must explore and address the barriers that marginalized and lower-status individuals experience in enacting their healthy intentions.