This article investigates how Information Systems researchers apply institutional theoretical frameworks. Our aim is to explore the operationalization of meta-theoretical frameworks for empirical research which can often present difficulties in IS research. We include theoretical, methodological and empirical aspects to explore modalities of use. After an overview of institutional concepts, we carry out a thematic analysis of empirical journal papers on IS and institutional theory indexed in databases from 1999 to 2009. This consists of descriptive, thematic coding and cluster analysis of this textual database; this combined qualitative and quantitative method offers a unique way of analyzing how operationalization is carried out. On the basis of thematic coding and cluster analysis, our findings suggest three groups of publications which represent different methodological approaches and empirical foci: 'descriptive exploratory approaches', 'generalizing approaches', and 'sociological approaches'. We suggest that these three groups represent possible patterns of the use of 'meta' social theories in IS research, reflecting a search for disciplinary legitimacy. This helps us analyze papers according to how they use and apply theories. We identify the "organizing vision" and the regulatory approach as two institutionalist 'intermediary' concepts developed by IS researchers. Furthermore, we find that institutional theoretical frameworks have been used in 'direct', 'intermediary' or 'combined' conceptualizations. We also confirm the dynamism of the IS institutional research stream, as evidenced by the increase in number of articles between 1999 and 2009, and identify a maturation process of the IS field in investigating a social theory. As a conclusion, we make suggestions to blend different conceptualizations, methodologies and empirical foci to enrich the use of institutionalist theories in IS empirical research.institutional theory in the IS field, the organizational level as the main unit of analysis, and quantitative research as the main research methodology mobilized. These two reviews do not focus on papers where institutional theoretical frameworks are combined with other theoretical frameworks, which we do in our literature review. Nor do they highlight how researchers applied the theories, which is the specific focus of our paper as we are interested in the theorization process itself. The main characteristic of our paper is its methodological approach which supports a deep analysis of this process in a specific body of literature. Another outcome is that we also provide a detailed analysis of the domain of institutional frameworks in IS research, covering a number of issues through the identification of categories and the proposition of a taxonomy.The first part of the paper introduces general institutional and neo-institutional theoretical frameworks. Its purpose is to provide sufficient detail to support the understanding and identification of uses of institutional theory in the IS research literature. N...