The thesis develops a sociological theory of strategy that is then applied empirically to nine firms within the Taiwanese PC industry. It aims to show why and how firms within the same industry and country pursue different strategies. This thesis begins by arguing the relative failure of economics to explain strategic difference because of the socially-embedded nature of economic action. This kind of argument calls for the use of sociology to analyse firm behaviour in order to help reconcile society with agency. Because society embodies a wide range of social structure, firms are able to draw upon a plurality of structural rules and resources in order to gain their strategic agency. Informed by this pluralistic account of economic action, the thesis goes on to suggest three sets of structural sources, namely, policy style, business recipe and technology paradigm. The patterning of the three structures constitutes an industry system which highlights the significance of social conflicts in structuring firm behaviour. In order to negotiate the conflicts, firms have to choose to conform to certain social structures. Here, choice is possible, because in the industry system there is more than one social structure providing social rules and resources for guiding and empowering firm behaviour. While recognising the possibility of choice, the thesis continues to argue that this agentive potential of doing otherwise is different for each company. The difference is a product of corporate identities which establish firnis' structural links with their attendant industry system and so provide them with both access to specific social resources essential to strategic choice, and certain particular rules about how to exercise their choices. Consequently, the concept of corporate identities provides an institutional linkage between structure and agency and it is through this linkage that we examine why firms make different strategic choices.