The well-known Prisoner's Dilemma (PD) is often used to model situations of social conflict between two or more actors. The essence of the dilemma is that each actor has individual incentives to act according to narrow self-interests referred to as defection, yet all actors are better off and receive higher payoffs for mutual cooperation. Many attempts have been made to study ways by which cooperation can be enhanced. This article focuses on a specific device, namely hostage posting or pledging of a bond. In the first part, a game-theoretic model is sketched that specifies the conditions under which hostage posting will effectively promote cooperative behavior. In the second part, the authors describe several experiments that were designed to test the descriptive power of the theory, and at the same time they provide further insight into the processes underlying social conflicts. Implications regarding social conflicts and possible applications to other domains are briefly discussed at the end.The well-known Prisoner's Dilemma (PD) is frequently used to model situations whereby the self-interests of an individual are in conflict with those of another individual or a larger group. Its popularity is based on (a) the assumption shared by most researchers that the reward structure of the PD is characteristic of a large number of socially significant real-life settings (e.g., Dawes, 1980;Pruitt & Kimmel, 1977;Rapoport, 1974) and (b) that the PD can be analyzed by a well-established formal theory, namely game theory. In particular, game theory can be used to specify the conditions under which "rational" individuals may choose between two possible acts: the adoption of an act that is best for the individual (disregarding the desires and goals of the other individual or the group), formally referred to as defection, or alternatively, the adoption of an act that is better for both the individual and the other person (or group) involved, formally referred to as cooperative behavior.It is important to emphasize the formal (conditionally) normative character of game theory. It specifies the optimal decisions to be taken by two or more actors, given that they are willing to adopt the underlying assumptions of the theory. The theory is not descriptive nor is it normative in the absolute sense. It only prescribes, under given assumptions, the best courses of action for the attainment of outcomes having certain formal optimum properties (Luce & Raiffa, 1957, p. 63). In the present context, the definition of a rational actor is limited to a person who is willing to adopt the underlying