In social theory, games are frequently presented as archetypal examples of activities governed by formal rules. Drawing upon ethnomethodology and figurational sociology, this project provides an analysis of the constituting of games and identifies the inadequacies of this conventional formalist wisdom. Applying and elaborating upon Garfinkel's work, two case-studies are presented which are designed to display the other dimensions of rule-following through which players accomplish a viable game. Analysis also reveals that this collaborative work does not preclude differing interpretations of the rules of the game. Changes to the rules are invoked in an attempt to remove their fringe of incompleteness in governing game-conduct and in the interests of creating and sustaining a viable game. These case-studies and a typification of game-rules provides the basis for analysis of the constituting of institutionalised 'invasion' games such as basketball, rugby union, soccer, rugby league, and netball. Interview material and documentary evidence is provided to argue that rule-changes are principally the outcome of a dynamic between legislators and players. Players explore the insufficiency of rules in precisely determining conduct in the game, and legislators respond by modifying the rules, to consolidate the game and thereby preserve characteristic features of game-identity and game-viability. This is elaborated by applying Elias's figurational analysis: changes to game rules are conceived as an unintended and unanticipated consequence of powerbalances and the different interests of the functionally interdependent groups who produce game-processes. By virtue of their separate functions in this process, each group seeks to mobilise their power and resources in pursuit of their interests in the game-process. Confirmation for the perspective upon game-constitution developed in this project is sought in an analysis of one contemporary initiative to establish an invasion game as constituted by a set of hybrid rules from Australian Rules and Gaelic Football. This analysis of game-processes and game-rules is designed to both exemplify and inform social theory, and also to make a significant contribution to sociological analysis of the development of contemporary sport.