Two sequential studies are presented that examine the validity of a set of environmental variables to predict heavy drinking at college students' most recent drinking occasions. Random telephone interviews (n=1609, n=400) of graduate and undergraduate students attending two large public universities in the southwestern United States were conducted during three separate surveys in 2000 and 2001. An original interview schedule was used and it included measures that examined environmental characteristics of students' most recent drinking events, motivations for drinking, demographics, and alcohol consumption. Using nonparametric exploratory and confirmatory discriminant analyses to distinguish between heavy episodic and non-heavy episodic drinking events, a discriminant function was identified that included the following environmental variables: (1) having many people intoxicated at an event, (2) having illicit drugs available at an event, (3) BYOB events and, (4) the playing of drinking games at the event. The validity of these environmental variables to predict heavy drinking among students was supported in a subsequent study examining a separate sample from the same student population. Environmental factors can be useful to predict heavy drinking events experienced by students. Prevention programs would benefit from targeting such factors in combination with more traditional individual-level approaches.