This survey article reviews the harvest of empirical world cities research since its formal inception about a decade ago. Taylor's (1997) delineation of ‘the problem of evidence’ in this literature is used as a cue to assess the merits and inadequacies of recent empirical studies. To get a handle on the literature as a whole, a taxonomy of empirical approaches is developed. Major features of the dominant approaches in general and some important studies in particular are discussed. This discussion is thereupon used to analyse the extent to which these studies have managed to construct meaningful measures of transnational inter-city relations. This analysis reveals that significant steps have been taken, but some new points of attention can be raised, such as the lack of suitable theoretical reference points in some recent empirical studies and the disproportionate focus on a relatively narrow range of formal economic processes.