This study attempted to identify factors associated with smoking onset among teens. It was hypothesized that initial cigarette smoking is largely prompted by peers, and that these prompts and subsequent social reinforcement may account for smoking participation. An in-depth structured interview investigating the first three smoking or smoking pressure experiences was conducted with 157 teens, including persistent experimental smokers (who smoked more than 10 cigarettes), minimal experimental smokers (who smoked less than 10 cigarettes), and nonsmokers. Analyses confirmed that prompting by peers is characteristic of a large majority of smoking onset situations. Initial situations are much more likely to involve others of the same sex. In roughly half of the incidents another young person was trying a cigarette for the first time. Persistent experimenters, when compared with minimal experimenters, were exposed to significantly more influences to smoke. These influences included modeling and social encouragement. Additional data suggested that persistent experimenters were more primed to smoke than minimal experimenters. For example, they had engaged in more premeditation, accepted offers to smoke with less hesitation, and inhaled more frequently. Also, pleasant emotional and physiological effects discriminated continuers from quitters. Nonsmokers appeared to possess more effective response strategies to refuse cigarettes. Implications of these data for prevention program design are discussed.