T'he South American genus Perissocentrus is revised. Six valid species are recognized, including P. argentinae, P. caridei, P. striatulus sp. nov. and P. tumidulus sp. nov. P. strialulus is described from a pupa of Cyanotricha necyria and as a parasitoid of the ichneumonid Casinaria cavigena on Leuculopsis pulverultenta. P. tumidulus was reared from Thanatospyche chilensis and Cercophana sp. P. porteri is given as a synonym of P. phormio. All species of Perissocentrus have been reared as pupal parasitoids of Lepidoptera, but 2 species are also facultative hyperparasitoids of Ichneumonidae. A key to males and females of the genus is provided. missing