This research offers several contributions to the study of organizational field construction by: highlighting power relations and the role of agents in the process of field construction; illustrating this process through the case of Orphan Drug field in the United States, and relating Bourdieuan concepts of field, habitus and capital to the current research in new-institutionalism in organizational analysis. It also shows that organizational field construction is a political and strategic activity which involves agents, possessing different capitals and endowed with different habitus, in a struggle for the legitimation and de-legitimation of alternative issues that may structure field construction process.