Three Cabus apella monkeys were infected with 3.5 x 10 sobre 5 cells of Trypanosoma cruzi Y strian in order to evaluate the parasitemia and to study the behavior of the parasites in the mammalian host for a one-year period. The parasitemia was determined by hemoconcentraction. In the there monkeys, circulating parasites were detected in blood one week after infection. Parasitemia persisted in two monkeys one year after infection, but not continuously. Cyclic peaks of parasitemia were not detected