This review concerns the importance of selfish genetic elements (SGEs) in speciation. We assess the importance of medea genes, meiotic drive elements, transposable elements and the bacterium Wolbachia in the creation of postzygotic isolation. Although all of these elements can contribute to postzygotic isolation, their contribution will often disappear if there is gene flow between the populations. Further, there is the possibility that incompatibilities produced by SGEs may lessen over time. We conclude that although some of the case studies are tantalizing, particularly those associated with Wolbachia, the role of selfish genetic elements in speciation remains unproven.