Chagas' Disease was first known in Argentina through lectures and demonstrations held by Lozano, Maggio and Rosenbusch. In 1914 Maggio and Rosenbusch verified for the first time the infestation of Triatoma infestans, one of the most abundant triatomids in Argentina, over almost all the country. In 1924 Mühlens et col. looking for malaria parasites in a collective survey found the first humans with S. cruzi in their blood. In 1926 Mazza found that the dog was naturally infected and diagnosed in 1927 the first human case showing the typical symptomatology decribed by Chagas but without micrographical proof of the etiology. In 1932 the first cases with the clinical features described by Mazza in Argentina were confirmed by him through positive blood microscopy. The number of cases found up to date is 1305 all of them etiologically confirmed by the M. E. P. R. A. The local origin by provinces is known of 1244: 341 (highest number) from Chaco; 322 from the province of Mendoza and 198 from the province of Santa Fé. Of the 1232 patients whose ages were known, 33 were fatal; of the these, 28 were children in early infancy, 16 of them under 6 months (57%); these represented 14% of all affected at that age (they were 85, giving 6.89% of the total number of cases) . The highest incidence was in children from 5 to 10 years (21.5% of the whole number) followed by the groups of from 2 to 5 years (20.21%) and of 10 to 20 years (20.12%).