The male postabdominal structures of the West Palaearctic species of the genus Tachina are described. A new identification key is given. Characters are illustrated by original pen drawings and deep focus micrographs, some of them for the first time. The results are documented by molecular analyses (based on CO°I, Cyt°b, 12S, and 16S rDNA). This approach solves old taxonomical discrepancies, which resulted in these conclusions: 1) the taxonomic concept ofthe genus was evaluated; 2) the position ofthe present subgenus Tachina s.str. seems to be untenable: T. grossa (Linnaeus, 1758) could be categorized inside existing subgenus Tachina s.str. and a new subgenus could be created for T. magna (Giglio- Tos, 1890); 3) an expected new species from subgenus Eudoromyia was confirmed; 4) T. nigrohirta (Stein, 1924) having been resurrected from synonymy was confirmed as a valid species; 5) some differences between central European and Japanese specimens of T. nupta (Rondani, 1859) were found.