The North American species of Udea are revised on the basis of about 2500 specimens, with strongest representation in the difficult itysalis group. Twenty-three species and an additional 19 subspecies are recognized. Of these, the following six species and 18 additional subspecies are described as new: U. washingtonalis hollandi, interior B.C. and Mont.; U. w. nomensis, Alaska; U. w. pribilofensis, Pribilof Is.; U. indistinctalis johnstoni, Wash., ? Sask.; U. brevipalpis, Colo., Utah and ? Calif.; U. cacuminicola, Colo., Wyo.; U. beringialis, Yukon, Alaska; U. derasa, B.C.; U. livida, B.C., Wash., Utah; U. turmalis catronalis, N. Mex.; U. i. tularensis, Tulare Co., Calif.; U. t. griseor, Calif.; U. itysalis mertensialis, N.S.; U. i. rindgeorum, Tooele Co., Utah; U. i. kodiakensis, Alaska; U. i. albimontanensis, Ariz., N. Mex.; U. i. durango, Colo., Utah; U. i. wasatchensis, central Utah; U. i. clarkensis, southern Nev., Calif.; U. i. marinensis, San Francisco Bay region, Calif.; U. abstrusa subarctica, Northwest Territories, Yukon; U. abstrusa abstrusa, Alta., Sask., Man.; U. a. cordilleralis, Wyo., Colo., Utah, N. Mex.; U. a. pullmanensis, Wash. Five nominal species are transferred from other genera to Udea: Botis octosignalis Hulst, from Pyrausta; Ebulea straminea Warren, from Calamochrous; Botis vacunalis Grote, from Pyrausta; Phlyctaenia rusticalis Barnes and McDunnough and P. berberalis Barnes and McDunnough. U. straminea (Warren) is synonymized with U. octosignalis (Hulst) and U. galactalis (Dyar) with U. vacunalis (Grote). U. turmalis (Grote) is separated specifically from U. itysalis (Walker). Phiyctaenia angustalis Barnes and McDunnough is transferred from Udea to Evergestis.