Decision making is a core feature of human life. A common problem that people often encounter over the course of life is what to do in the event of sickness. Since illness has a major influence on people’s lives, studying healthcare-seeking is of vital importance. Moreover, patients’ decisions about healthcare fundamentally determine the performance of the overall healthcare system in terms of a population’s health, the quality of healthcare services, and the level of expenditures. Even though illness behaviour has been an intensively studied research topic over the past five decades, previous work has largely overlooked the embeddedness of these decisions in social and institutional contexts. This project will theoretically, methodologically, and empirically enhance previous research. The project will contribute to the development of an integrative theoretical framework of illness behaviour and provide an important test case for institutional theories and the theory of frame selection. The collected survey data on people over 65 will provide a unique data source about the healthcare needs of older people and the way they manage these needs. It will analyze these people’s decision making when having a medical condition with a particular emphasis on the interpretation of symptoms and the utilization of healthcare, and it will generate information about the extent and variety of self-care strategies. Finally, the project will analyze how social networks and institutional features of the healthcare system influence the decision making of healthcare seeking.