The systematics of the genus Zabrus Clairville, 1806 is currently based on morphological characters that show a high degree of parallelism. The aim of this study is to find new characters in the female genitalia, which give a better understanding of the phylogeny of the genus and result in a new classification based on monophyletic taxa (subgenera and species groups). For this purpose slides of the whole female reproductive tract were studied under light microscopy and the gonocoxa IX under scanning microscopy. The study of species belonging to eight subgenera of Zabrus, and of twelve subgenera of its sister taxon Amara, shows that Zabrus is characterised by the lack of a spermatheca. This apomorphy is reported for the first time in carabids, and corroborates the monophyly of the genus in comparison to Amara. A villous canal that is intimately joined to the distal bursa copulatrix was found in both genera and in species of related tribes. This feature could be an apomorphy of the Harpalidae sensu Deuve (1988). However, only in Zabrus does the villous canal end in a long falciform head, which is probably another autapomorphy of the genus. It is postulated that the primitive bursa copulatrix of the genus was made up of a moderately inflated basal half and an elongated and simple distal half. This pattern is found in species of the subgenus Zabrus, which are widely distributed, and the subgenera Euryzabrus, Platyzabrus, and Epomidozabrus, which are endemic to the Iberian Peninsula. Extra lobules arising in the region where the two parts of the bursa meet, and cup-like infoldings of the distal bursa are possible apomorphic states that characterise the subgenera Pelor and Iberozabrus. Gonocoxite 2 does not have the strong and short spines found in species of related taxa. Differences in size and shape of both gonocoxites, distribution of setation and microtrichia, and presence of furrow "pegs" are characters of potential phylogenetic interest, which should be thoroughly investigated in other subgenera.