The Flat-footed Flies (Diptera: Opetiidae and Platypezidae) of Europe presents a detailed account of the taxonomy, biology and distribution of the 44 European species of Opetiidae and Platypezidae. Two of these are here described as new to science. Known larvae develop in the larger fungi; adults are honey-dew feeders on broad leaves. Both families are characterised and proposals on their relationships and phylogeny are discussed. All European species are keyed and described in detail. Adult and larval biology are reviewed. The provincial distribution of 35 species occurring in Fennoscandia and Denmark is listed in a detailed catalogue. The work presents identification keys to genera and species and for each species descriptions and accounts of its nomenclature, biology and distribution. Known early stages are keyed to genera and described under each species.