Resistance to insecticides is considered as a barrier to chemical control of Triatoma infestans, the main vector of Chagas disease in the Southern Cone of South America. Although initiatives of disease incidence reduction in the area have integrated different strategies, they have been based mainly on vector elimination through pyrethroids insecticides like deltamethrin. The first reports of pyrethroids resistance were found in T. infestans populations from Salvador Mazza (northern Argentina) and Yacuiba (southern Bolivia). Recently, a mosaic pyrethroid resistant focus was described in the center of the Argentine Gran Chaco (General Güemes department, Chaco province), characterized by the presence in the same area of susceptible and very high resistant populations.