This article introduces a typology and evaluates a set of measures for studying professional and administrative models of organizing. Four mental models of organizing are contrasted: the bureaucratic system model, the market enterprise model, the professional group model, and the community service model. These organizing models reflect the internal and external partitioning of administrative and professional rationality. This article describes the development of an instrument for measuring the extent to which individuals perceive that their organization does or should emphasize each of these four models. Data obtained from repeated administrations of this survey instrument in a managed health care organization support the convergent and discriminant validity of the proposed measures, as well as their temporal stability and generalizability across occupational groups. An analysis of relationships between these constructs and theoretically related constructs provides preliminary evidence for their value in the analysis of complex organizations.