The differences among the four education systems of the UK are often perceived as a nuisance by comparative researchers. This paper argues that they are also an opportunity. It describes the four systems and summarises their similarities and differences. It then presents Jive reasons for giving 'home international' comparisons a more prominent role in comparative research. These are, respectively: their potential contribution to theoretical debates; specific differences among the four systems, which touch on core problems of educational research; the practical value of home international comparisons; their potential for policy learning; and the relative ease of conducting them.