We make a three-fold contribution to research on the European radical left. First, we will offer a clear and comprehensive definition of the term ‘radical left’. Second, we will look at the main developments within the European radical left as a whole, and not just at one sub-set of political parties. Third, we will take a pan-European perspective, focusing on both Eastern and Western Europe. The radical left in Europe post-1989 is both in decline and in mutation. Decline is evident in both the marginalization and moderation of Communist organizations (notably parties), a direct result of the fall of the Soviet Union, and the fissiparous nature of many radical left groupings. But the end of the USSR has also given space for mutation, that is, the emergence of a New Radical Left employing ‘new’ ideological approaches (principally ‘social-populism’) and modern forms of trans-national cooperation (particularly through the European Parliament and the ‘antiglobalization’ movement). This mutation indicates future potential, however unrealized so far.