In a representative sample of 178 students at a small liberal arts university, 23 percent of women and 7 percent of men surveyed reported one or more experiences of unwanted sexual intercourse. Seventy-eight percent of unwanted vaginal, anal, and oral incidents took place while - "hooking up," - whereas 78 percent of unwanted fondling incidents occurred at parties or bars. The most frequently endorsed reason for unwanted sexual intercourse was impaired judgment due to alcohol. The most frequently endorsed reason for unwanted fondling was that it happened before the perpetrator could be stopped. Of those affected by unwanted sexual intercourse or unwanted fondling, 46.7 percent and 19.2 percent reported unwanted memories, 50 percent and 32.7 percent reported avoidance and numbing responses, and 30 percent and 26.9 percent reported hyperarousal responses, respectively. A preliminary model of unwanted sex and collegiate social dynamics is proposed to provide a heuristic for further research. Tables and references (Published Abstract)