The dissertation provides a rich analysis of routines in four case-study companies. Explanations for the behaviour of the firms are developed and provide new building blocks for the understanding of other firms in different circumstances, emphasising empirical evidence, rule-based action and recognising the historical, social and interpretive contexts. Routines are defined as established, significant, sanctioned and recurrent practices within organizations. A number of key features of organizations figure in the analysis: the relationship between structure and agency, the firm's culture and the firm's history. Structures are identified as rules and relationships. The analysis of agency focuses on the position of the agent, the agent's skill and the desire to reduce uncertainty. Technology is an important factor in the analysis. It is (partly) constitutive of the firms, that is it has the power to enact or establish the firms. It cannot do this on its own, it is argued, but, in interacting with other factors, has major implications for the structure and routine behaviour of the firms. The cases suggest that technology has implications for human agency which go beyond the initial intentions of the agents. Technology is not determining but interacts with the other factors in a recursive way and cannot be adequately analysed outside the social system of which it is a part. The primary contribution of the research is the development of a broader concept of routine, in particular, the identification of routine practices at a strategic level and the demonstration that such practices can incorporate change. In addition, the analysis identifies the role of technology in economic change. It adds to the understanding of routines more generally and confirms that an institutional approach to the understanding of firms' behaviour is fruitful and can add to the current repertoire of approaches in Economics.