The purpose of this review is to further our knowledge about what is meant by inclusion in research addressing the topic. While it is common to remark that inclusion is defined in different ways in research, few attempts have been made to map and analyse different types of definitions and whether there are patterns to be find in how the concept is used. The 30 most cited journal articles from a North American and a European research arena were selected for analysis. Each article was analysed in relation to genre, theoretical tradition and inclusion concept used. The review yielded several important results. To name a few, a divide was identified between position articles, with developed discussions about and analyses of the meaning of inclusion, and empirical articles, where inclusion signifies that children with disabilities are placed in the mainstream. In addition, writing within a critical theoretical tradition was much more common among positional papers. Further, both arenas are dominated by Anglo-Saxon researchers. It is argued that the conceptual confusion characterising the field impedes its development.