College students' processing of alcohol social norms messages, related effects on normative judgments, attitudes toward their own behaviors, and perception of undergraduate attitudes were examined using expectancy violation theories and social norms marketing. Data were collected from 2 universities (N = 393). Following message exposure, the majority moved their normative judgments toward the statistic provided in the message. Slight attitude change occurred but not always in the desired direction. Those most likely to develop unhealthier attitudes drank more than those who developed healthier attitudes, consistent with psychological reactance to the messages. Therefore, the effects of social norms campaigns on those at greatest risk for primary and secondary alcohol effects due to their increased alcohol consumption could lead to increased risk for those participants, indicating that the widespread use of social norms campaigns needs to be scrutinized.