Alongside the growing numbers of professional doctorate programmes being offered within universities in the past 20 years, there has been a growth in the academic literature associated with various aspects of these research degrees. This systematic literature review draws on the evidence of 193 academic papers to map out the existing academic knowledge about professional doctorates and highlight the gaps that this special issue aims to address. We use a simple vote-counting approach to categorizing the identified papers, considering: the type of professional doctorate studied, the country in focus, the main themes explored, the research methods used and the year of publication. This review highlights the need for academic work in this area to move beyond individual case studies of practice on programmes towards developing principles of practice for professional doctorates as a whole. This special issue hopes to start that academic conversation.