The monograph gives a theoretical explanation of observed cooperative behavior in common pool situations. The incentives for cooperative decision making are investigated by means of a cooperative game theoretical framework. In a first step core existence results are worked out. Whereas general core existence results provide us with an answer for mutual cooperation, nothing can be said how strong these incentives and how stable these cooperative agreements are. To clarify these questions the convexity property for common pool TU-games in scrutinized in a second step. It is proved that the convexity property holds for a large subclass of symmetrical as well as asymmetrical cooperative common pool games. Core existence and the convexity results provide us with a theoretical explanation to bridge the gap between the observation in field studies for cooperation and the noncooperative prediction that the common pool resource will be overused and perhaps endangered.