The positive outcomes of coordination of healthcare services are to an increasing extent becoming clear. However the complexity of the field is an inhibiting factor for vigorously designed trial studies. Conceptual clarity and a consistent theoretical frame-work are thus needed. While researchers respond to these needs, patients and providers face the multiple challenges of today's healthcare environment. Decision makers, planners and managers need evidence based policy options and information on the scope of the integrated care challenges they are facing. The US managed care organization Kaiser Permanente has been put forward as an example for European healthcare systems to follow, although the evidence base is far from conclusive. The thesis has five objectives: 1) To contribute to the understanding of the concept of integration in healthcare systems and to identify measurement methods to capture the multi-dimensional aspects of integrated healthcare delivery. 2) To assess the level of integration of the Danish healthcare system. 3) To assess the use of joint health plans as a tool for coordination between the regional and local level in the Danish healthcare system. 4) To compare the inputs and performance of the Danish healthcare system and the managed care organization Kaiser Permanente, California, US. 5) To compare primary care clinicians' perception of clinical integration in two healthcare systems: Kaiser Permanente, Northern California and the Danish healthcare system. Further to examine the associations between specific organizational factors and clinical integration within each system. The literature was systematically searched to identify methods for measurement of integrated healthcare delivery. A national cross-sectional survey was conducted among major professional stake-holders at five different levels of the Danish healthcare system. The survey data were used to allow for analysis of the level of integration achieved. Data from the survey were additionally used to investigate the use of joint health planning as a tool for coordination of regional-local healthcare delivery. Analysis of secondary data from the Danish healthcare system and Kaiser Permanente, California were used to compare population characteristics, professional staff, delivery structure, utilisation, quality measures and direct costs. A cross-sectional survey among primary care clinicians in Denmark and in Kaiser Permanente, Northern California was completed to allow for comparison of clinical integration in the two systems and system specific associated factors. In this thesis a conceptual framework and a model for assessment of the conditions for integrations as an intermediate healthcare system outcome are presented. Furthermore, the results show that integrated healthcare delivery can be measured: 24 methods are available and some are highly developed. However, the field is still in its early phase and guidelines for how to proceed are devised. It was confirmed on a national level that integration of care is a widespread challenge, and that only half or less than half of patients in need of integrated services receive such care. Options for decision makers and managers are discussed. From a theoretical perspective joint health plans as applied in Denmark do not match the degree of complexity in the healthcare system. It was therefore in agreement with the theoretical findings when major stakeholders agreed that the joint health plans had not been effective as a tool for coordination. Joint health planning processes should actively engage all stakeholders and a high degree of recurrent feedback are warranted. When comparing Kaiser Permanente, California with the Danish healthcare system, our study suggest that Kaiser Permanente has a population with more documented disease and higher operating costs, and performs better than the Danish healthcare system on the observed quality measures. Substantial differences were found in the perception of clinical integration in the two settings. More primary care clinicians in the Northern California region of Kaiser Permanente reported being part of a clinical integrated environment than did Danish general practitioners. By measuring the level of clinical integration in Kaiser Permanente using the Danish healthcare system as a point of reference our findings support the literature that points to the importance of integrated healthcare delivery as a driver for the performance results of Kaiser Permanente. However caution must be advised before making concrete conclusions due to the complexity of the matter and until more studies have been conducted. With this thesis an initial step has been taken into a new research field. Ongoing research will make it possible to deliver the evidence needed by decision makers, planners and managers - ultimately to benefit the patients.