Since the Salamanca Statement was published in 1994 a massive amount of research has addressed the issue of inclusive education. Yet, there is a sense of lack of progress which seems to necessitate a critical look at the field while not neglecting advancements made. Such advancements concern the development of theory, a concept which is given a broad interpretation in the paper. Both theories with limited scope and more encompassing theories have been developed. However, from the point of view of Lewin´s well-known formulation 'there is nothing as practical as a good theory' there seems to be a lack of theories that have empirically been shown to be successful tools in the development of more inclusive school systems, schools and classrooms. The case study seems to be a methodological approach well suited for the development of such theories. Two examples from Sweden, one from the school level and one from the classroom level, are used to illustrate the potential of case-studies to develop theory in this area of research.