Subject collaboration is a working method for teachers that is stated in the school's governing documents. The study has aimed to put subject collaboration with religious education in a context and investigate what subject collaboration looks like in practice, as well as some underlying factors that enable subject cooperation. The goal is to be able to identify keys that can contribute to increasing knowledge about subject collaboration regarding religious education. To study subject collaboration and its key factors, the study includes a qualitative and quantitative survey conducted in two municipalities. In the background, the reader is given a historical curriculum overview starting in Lgr62 and reaching to the current Lgr22. The overview shows that the presentation of policy documents concerning subject collaboration has changed over time. Previous research has highlighted the subject based on different aspects such as the opportunities and difficulties collaboration between subjects can entail, and external factors that can counteract or promote subject collaboration. The theoretical framework for the study is based on social and group psychological theories and concepts. The theoretical starting points for understanding and discussing subject collaboration are: social cognitive theory; social exchange theory; individual and group; cooperation and competition; goals and motivation. The theories are used to shape the starting point for the interpretation that is then made of the empirical evidence. Some key concepts used in the work are subject collaboration and key factors. The results show that the correspondents have a positive attitude towards subject collaboration, but besides the promising approach, collaboration generally takes place to a low extent, regardless of subject. The correspondents consider both the management and themselves to be ultimately responsible for the practice of subject collaboration. The results show that there are key factors. These factors both inhibit but also enable subject collaboration with religious education. These key factors have been categorized in three themes: attitude, organization and knowledge.