Game Theory describes human interaction involving conflict, cooperation and competition, the term Interpersonal Decision Theory is synonymous. The term reflects the fact that most essential features of this field are manifested in parlor games. This topic-level treatment covers large parts of the basic concepts and methods and sketches some fields of recent applications. The simultaneous occurrence of strategic, stochastic and dynamic phenomena, the fundamental role of epistemic aspects like knowledge and information and the impact of institutional and organizational structures make game theoretic analysis a highly complex task. -- allocation ; apportionment ; Aumann economy ; axiomatic approach ; balanced games ; bargaining solution ; characters ; coalitional form ; convex games ; cooperative game ; coordination game ; core ; cost sharing ; directed games ; equivalence principle ; exchange economy ; extensive form ; evolutionary stability ; fictitious play ; game form ; homogeneous games ; implementation ; incentive compatible ; Kalai-Smorodinsky solution ; knowledge ; LP-game, Maschler-Perles solution ; mechanism ; modiclus ; Nash equilibrium ; Nash solution ; normal form ; nucleolus ; outcome function ; payoff function ; reduced games ; repeated games ; revelation principle ; Shapley value ; simple games ; social choice rule ; TU-game ; vNM-Stable Set ; voting games ; Walrasian equilibrium