AbstractUroleuconis one of the largest genera of Macrosiphini, with 216 known species; it is one of the few genera of Aphidinae to have a diversification in South America, with 15 native species and 1 subspecies. Moreover, 7 introduced species have been recorded in South America. Five new species from Argentina are described herein:Uroleucon malarguenseOrtego and Nieto Nafría,sp. nov.,U. mendocinumMier Durante and Ortego,sp. nov.,U. patagonicumNieto Nafría and Seco Fernández,sp. nov.,U. payunienseOrtego and Nieto Nafría,sp. nov., andU. riojanumNieto Nafría and Mier Durante,sp. nov.One Palearctic species,U. jaceae(Linnaeus), has been recorded for the first time in South America, and thus 28 species and 1 subspecies are now known from South America.Uroleucon essigiCarvalho andU. chilense(Essig) are recorded for the first time from Argentina, and 20 of these 29 taxa are known for this country. New morphological and bionomic data from some previously known species are given. Alate viviparous females ofU. gochnatiaeDelfino and oviparae and males ofU. bereticum(Blanchard) andU. macolai(Blanchard) are described. A taxonomic discussion about native South American species ofUroleuconis given, and we include them at present in the subgenusLambersius. A key is provided for the identification of apterous and alate viviparous females.