ABSTRACT: In considering the use of estuarine habitats by fish assemblages, alternative views of the assemblage are increasingly being explored, based on functional rather than taxonomic aspects. The allocation of all taxa to a number of functional guildsallows a description of fish assemblages in terms of vertical zonation, habitat preferences, including the substratum preference of benthic/demersal species, and dietary preferences. This paper presents the first comparison of the structure of the fishassemblages in the tidal marshes of 6 European estuaries (Bay of Cadiz, Spain; Mira, Portugal; Loire, France; Westerschelde, The Netherlands; Humber, UK; Forth, UK). Cluster analysis was used to compare the assemblages recorded in 29 tidal marsh andassociated estuary reference sites. Distinct differences between estuaries were apparent in comparing the taxonomic structure (species, family) of the assemblages, indicating a division between assemblages of northern and southern Atlantic European tidalmarshes. The use of ecological guilds successfully separated marsh assemblages dominated by freshwater adventitious/diadromous taxa (Loire) from those dominated by marine juvenile taxa (Mira, Forth). Comparisons of vertical distribution guilds indicated amajor division between pelagic-dominated (Forth, upper Loire) and benthic-dominated (Cadiz, Westerschelde, Mira, Loire) assemblages. This division was also partly reflected by the dietary preference guilds, with a strong separation between assemblagesdominated by planktivores (Forth) and those in which most taxa are either invertebrate feeders (Humber, Cadiz, Westerschelde) or invertebrate/fish feeders (most Mira sites, lower Loire). The very low representation of a primarily piscivorous guild in allsites (in contrast to the fish assemblages of the main estuaries) supports the view that European tidal marshes contain fish assemblages with high proportions of juvenile individuals and may provide significant refugia for life stages vulnerable topredation. Although the comparability of datasets is limited by differences in sampling regimes and methodologies, the use of functional guilds, reflecting different aspects of the use of the marshes, reveals that functional similarities exist between thefish assemblages of European tidal marshes, despite considerable taxonomic, physical and chemical differences between the sites. Further modifications to the use of functional guilds are discussed, and recommendations made to refine their value forstudying fish assemblages in tidal marsh environments.