Two year old Cebus sp monkeys were infected with the Argentine strain of T. cruzi by the conjuctival route employing metacyclic forms of the parasite, obtained from dejecta of T. infectans. Both animals developed parasitemia detected by xenodiagnosis, without any overt acute disease, and with serological conversion. After 9-10 months of infection, both animals developed significant ECG abnormalities. One animal died spontaneously and the other was sacrificed. At necropsy, both animals presented significant megacolon. Severe thinning of the intestinal wall was observed without inflammatory lesions and with preservation of the parasympathetic plexus. Histologic studies revealed fibrotic lesions in the myocardium. In this organ, lymphocytic infiltrates were found in infrequent and small foci, but no pseudocytic forms containing parasities were observed. These observations suggest that the Cebus monkey may be a useful experimental model for some major aspects of chronic Chagas disease in man.