Fourteen species and four genera are treated here. Of these, one genus and one species are described for the first time. Most of the other North American species are redescribed, wherever it was possible to obtain specimens from which to make the descriptions. The genus Epirhyssa has been abandoned, as it did not seem to have distinctive generic characteristics to separate it from Rhyssa. A new genus Pseudorhyssa has been established. Its transversely wrinkled mesonotum places it within the scope of the genera treated here; the entire sternal plates of its abdomen, however, separate it from the other genera. The type of this genus, Pseudorhyssa sternata is here described. The description of Thalessa histrio, an unlocated species, is also included.