By means of a literature review,this paper strives to provide some clarity on the much-debated relationship between product market competition and firms' incentives to innovate.It shows that in the literature there does not exist a robust relationship between competition and incentives to innovate.Therefore,it would be futile to continue the debate over whether competition stimulates or hinders innovation.A more useful approach is to make a distinction between pre-innovation competition and post-innovation competition,as it provides a way for reconciling many of the seemingly contradictory findings from the literature.Another important insight from the literature is that the relationship between competition and innovation depends on the source of increased competition.