The noctuid subfamily Heliothidinae, which is represented in North America by 158 species, is redefined, largely on the basis of male genitalic characters. Of genera included in the subfamily in McDunnough's 1938 check list, only four are recognized as valid, these being Heliothis Ochs., Schinia Hbn., Heliolonche Grt., and Melaporphyria Grt. Helicoverpa Hdwk., which was described subsequent to the appearance of McDunnough's list, and Protoschinia which is described as new here, are also included. Grotella Harv., Hemigrotella B. & McD., and Neogrotella B. & B. are not considered heliothidine genera and are removed to the Stiriinae.Eight genera, which have been assigned to the Amphipyrinae because they lack the mid and hind tibial setae characteristic of other heliothidine components, have also been incorporated in the Heliothidinae; these genera are Microhelia Hamp., Heliothodes Hamp., Baptarma Sm., Eutricopis Morr., Derrima Wlk., Erythroecia Hamp., Rhodoecia Hamp., and Pyrrhia Hbn. Because of the close similarity in structure and habits between these genera and those previously mentioned, the two groups are considered to constitute a monophyletic assemblage within the Noctuidae, despite the discrepancy with respect to mid and hind tibial setae.A key to the 14 North American genera of the Heliothidinae is presented. Descriptions of genera and figures of the male and female genitalia of the type species of all valid genera and of many genera in synonymy are provided. Canthylidia Butl. and Timora Wlk. are newly synonymized to Heliothis, and Heliosea Grt. to Heliolonche Grt. A check list of the North American Heliothidinae is appended to the text.The possible phylogenetic relationship of the Heliothidinae to the Stiriinae is discussed. The latter group is raised from tribal rank in the Amphypyrinae to subfamily rank; a number of genera are added to it, and a provisional redefinition of the subfamily is presented.