A provisional cladistic analysis of the species groups of Gonatocerus Nees is presented, based on 24 characters. Six species groups are defined, but only the four Nearctic ones are described. The species groups proposed are the ater, deficiens, litoralis, membraciphagus, straeleni, and sulphuripes groups. The ater group is divided into the morrilli, ater (s.s.), and bucculentus subgroups. Keys are provided to distinguish the species groups, and females of the sulphuripes- and ater-group species. Twenty-four species are recognized in the sulphuripes and ater groups for America north of Mexico. Eight species are recognized in the sulphuripes group, of which californicus, koebelei, maga, mexicanus, rivalis, and utahensis are redescribed. Two species, floridensis and lissonotus, are described as new. One new synonymy is proposed: titillatus is considered a junior synonym of utahensis. Sixteen species are recognized in the ater group, of which ashmeadi, capitatus, dolichocerus, fasciatus, latipennis, morrilli, novifasciatus, ovicenatus, and triguttatus are redescribed. Seven species, bucculentus, enicmophilus, flagellatus, impar, incomptus, inexpectatus, and inflatiscapus, are described as new. Two new synonymies are proposed: maximus is considered a junior synonym of latipennis, and marilandicus a junior synonym of dolichocerus. Lectotypes are designated for ashmeadi, capitatus, koebelei, mexicanus, morrilli, ovicenatus, triguttatus, and utahensis.