The phylogeny of Syllidae is assessed in two parsimony analyses of 107 morphological characters. The first analysis included one species of each of the 71 genera of the Syllidae, as well as members of other close families. In the second analysis, 23 poorly known genera were excluded. Character information is based on the examination of available types, additional non-types and newly collected material. Syllidae, except Bollandia Glasby, 1994 is monophyletic. Both analyses supported three of the four traditional subfamilies (Exogoninae, Syllinae and Autolytinae) as monophyletic, whereas Eusyllinae was clearly a polyphyletic group. The genera Anoplosyllis Claparede, 1868, Astreptosyllis Kudenov & Dorsey, 1982, Streptosyllis Webster & Benedict, 1884, Streptospinigera Kudenov, 1983 and Syllides Orsted, 1845 comprise a well-supported monophyletic group, which we classified as a new subfamily: Anoplosyllinae n. subfam. Our results indicated high levels of homoplasy in the morphological characteristics that traditionally used to differentiate groups, such as the fusion of palps and the presence of nuchal epaulettes. Considering the reproductive modes, schizogamy has appeared twice in the family as the derived condition evolving from epigamy, and Exogoninae may be divided into two monophyletic groups based on the brood system.
