The propensity to cooperate in single plays of three game structures (chicken, no conflict, and prisoner's dilemma) under two conditions of commitment to future interaction, using two experimental environments, was investigated. In addition, the effects of negative payoffs and the opportunity to maximize relative rather than absolute gain were examined. The results showed that committed subjects were more cooperative in all three structures than were uncommitted subjects. The propensity to cooperate was greatest for the no conflict structure, weakest for the prisoner's dilemma structure, and intermediate for the chicken structure. The largest difference between committed and uncommitted subjects in the propensity to cooperate was observed for the prisoner's dilemma structure. A comparison of these results with repeated play studies supports the use of single play studies of social interaction for analyzing the effects of social structure on behavior.