An intervention to reduce college alcohol use and secondhand effects was tested. Freshmen dormitory wings at a large Mid-Atlantic public university were assigned to single-gender (SG) or mixed-gender (MG) Information-Motivation-Behavior (IMB) workshops implemented during the first weeks of school, or a control condition. Students were surveyed before school began and at 2- and 6-month follow-up. Analyses indicated that, among males, the adjusted mean weekly alcohol use was lower in the SG than the control condition (1.89 vs. 2.72, p = 0.041). Among females, the adjusted mean weekly alcohol use was lower in the MG than the SG (1.60 vs. 2.44, p = 0.021) and control condition (1.60 vs. 2.27, p = 0.056). Further research should identify underlying mechanisms for effective alcohol behavior change among male and female wing-mates. (Contains 2 tables and 2 figures.)