Species of Entedon having a frontal fork with impressed arms extending to the eyes are reviewed and a key is given. Most but not all species having this character belong to the species-group of Entedon cioni which is redefined to exclude apparently unrelated forms. The reliability of certain specific characters is assessed, and in an account of the biology of Entedon it is proposed that their koinobiotic development is conducive to a narrow host range. Taxonomic, biological and distributional data are given in a check-list to Palaearctic and Nearctic species assigned to the species-group of E. cioni. Four new species of Entedon are described: E. incultus sp. n. and E. setifrons sp. n. from Britain and E. oxys sp. n. from Spain belong to the cioni species-group; E. albiscapus sp. n. from France is an isolated species.