The authors examined 3 possible explanations for the failure of a social norms campaign at a large public university. They administered an anonymous survey to 2 random samples of undergraduate classes: a baseline assessment of 616 students before the campaign's implementation and a follow-up survey of 723 students 4 academic years later. At follow-up, 66.5% of the students were aware of the campaign, yet the survey revealed no reduction in perceived drinking norms or alcohol use in this group. An analysis of the postcampaign sample revealed that (1) a majority of the students did not find the statistics used in the campaign messages credible, (2) higher levels of alcohol use predicted lower levels of perceived campaign credibility, and (3) only 38.5% of the students understood the campaign's intended purpose. If they are to influence personally relevant drinking norms, these campaigns must undergo further development to enhance message credibility and participants' understanding.Key Words: college drinking, social norms model