Groups of taxa of the polychaete family Nereididae were studied with the aim of presenting a revision of the subfamily Nereidinae. Detailed description of characters starting with a selected group, Neanthes, was extended to include a wider range of species level taxa to include as much variation in morphological characters as possible. Description of morphological characters and taxa were systematised in a database of Nereididae using the DELTA (DEscription Language for TAxonomy) system. Based on this database an interactive key of selected taxa is presented. A dataset of 86 characters for 51 taxa were analysed with parsimony methods to test if heterogeneous large genera like Nereis, Neanthes, Ceratonereis and Perinereis were natural groups, and to revise genera in Nereidinae. Although the analyses due to large amounts of homoplasies failed to give results that a complete revision of genera could be provided, they showed that the large genera are not monophyletic groups, and that previous attempts to group species into informal groups based on morphological characters not always are supported. The ingroup could not be grouped as monophyletic, hence suggesting Nereidinae is not a natural group. The results and levels of homoplasy made it impossible to undertake further analyses and provide a revision as such of Nereidinae. Cladistic analyses of a resulting clade from the consensus Nereidinae tree verified the monophyly of Pseudonereis including all 11 taxa considered valid, and a revision of the group including redescriptions of all taxa based on type material could be done.