Organisations that are dependent on external settings, among them political, need to understand the logics that shape their environment. The professionals in medical and dental organisations are used to decision-making processes based on “science logics” wherein each step is transparent and steps follow each other in a predictable manner. Political decision-making is often not possible to understand from that background, and Olsen (1972) described an alternative model of non-rational decision-making, the “garbage can model”. In this a decision will be made only when four “streams” of requisites are present at the same time. These are streams of 1/ problems to be solved, 2/ solutions, 3/ choice opportunities, and 4/ decision-makers. Aim. The aim of this study was to describe some changes in the National Dental Insurance (NDI) that is an important part of the environment for dentistry in Sweden, and to analyse the underlying political logic. Method. The description was made from backgrounds in official documents and proposals to reform the NDI and these descriptions were analysed using theories from decision-making. Results. The objectives in the NDI changed from a formal emphasis on prevention to an insurance against high cost for specified groups of patients. These changes were in contradiction to the stated objectives in the reformed NDI. These changes can be better understood by using a non-rational model of decision-making. Conclusions. The “garbage-can” model for decision-making can be used to gain a better understanding of the logics in the political system that forms the environment for a care organization.