In recent years researchers have paid substantial attention to the issue of college students' alcohol use. One limitation to the current literature is an over reliance on retrospective, self-report survey data. This article presents field methodologies for measuring college students' alcohol consumption in natural drinking environments. Specifically, we present the methodology from a large field study of student drinking environments along with some illustrative data from the same study. Field surveys, observational methods, sampling issues, and breath alcohol concentration sample collection are detailed. (Contains 4 figures and 2 tables.) [Funding for this study was provided by the National Institute for Alcoholism and Alcohol Abuse (RO1 AA013968). An earlier version of this paper was presented at the annual meeting of the Society for Prevention Research and the Research Society on Alcoholism (2005).]