While there is a growing awareness of the 're-emergence' of working poverty, this topic remains relatively under-researched. This article provides an encompassing review of the literature dealing with the situation in Europe, North America and the Antipodes, with a focus on the theoretical models found in this literature, the definitions used and the risk groups identified. The main conclusion is that most publications were not based on a specific theoretical model, which has led to a flurry of definitions; moreover, conclusions on certain risk groups are divergent. The end of the article focuses on what remains to be done, because there are good reasons to think that working poverty might become a more pressing problem in the near future, and social policy researchers will have to have good theoretical frameworks and robust evaluation strategies in the years to come.