Research to date has documented weak or inconsistent associations between market and organizational factors and the adoption of physician-organization arrangements (POAs) (e.g. physician-hospital organizations, management service organizations and independent practice associations) designed to increase physician integration. We argue that POAs may mask considerable variation in how these entities are operated and governed. Further, because the operating policies and practices of POAs are likely to influence more directly the behaviour of physicians than the structural form of the POA, they may be more sensitive to the market and organizational contingencies that encourage integration. This study attempts to test empirically the relative effects of POA type and market, strategic and organization factors on the operating policies and practices of market-based POAs. Results suggest that type of POA, and market, strategic and organizational factors affect risk sharing, physician selection practices, physician monitoring practices and ways in which monitoring information is used to influence physician behaviour in POAs.