While developing a data base for phylogenetic analysis of the New World streptocephalids we compared them with species from Africa, Europe, and India. In doing this, we found that the morphology of the peduncle of the distal antennal outgrowth and the biramous ovaries developed in seven North American species can contribute to the systematics of the genus. Thus, our investigation consisted of (1) a review of the external morphology of the antenna, (2) biometry of selected parts of the antenna to obtain informative ratios, (3) a review of the presence or absence of genital linguiform outgrowths, extension of the non-retractile parts of the penes, and general morphology of the cercopods, (4) a study of the location of the ovaries, and extension of the brood-pouch. On the basis of the results we classify Streptocephalus into nine species groups. Five subgroups are identified within two of the species groups. Several implications of the present approach are discussed.