Twenty four Cebus apella monkeys were studied as a biological model for the cardiac chronic form of Chagas' disease. Twelve were inoculated with Trypanosoma cruzi trypomastigotes, seven with the Brazilian Y strain and five with the Argentinian RA strain. Twelve monkeys were uninfected controls. The following parameters were studied: body weight, body temperature, direct parasitemia, xenodiagnosis, specific antibodies by IFA, clinical chemistry, hematology, ECG and chest X-ray. Three monkeys infected with Y strain were sacrificed at 4 months and 4 monkeys at 12 months after inoculation. Monkeys inoculated with RA strain were sacrificed at 48 months. Direct parasitemia was positive within a week after inoculation in all monkeys. Xenodiagnosis was positive until 49.0 +/- 3.0 and 79.0 +/- 6.0 weeks p.i. for Y and RA strains, respectively. In all inoculated monkeys an increase in antibody titers was detected within 3 weeks after inoculation. In all monkeys inoculated with the Y strain and 3/5 with the RA strain abnormal ECGs were observed within 1 or 2 weeks p.i., becoming more severe in the chronic phase. Y strain inoculated monkeys sacrificed at 4 months presented only a slight concentric hypertrophy of the heart left ventricle. Those sacrificed at 12 months had concentric left ventricle hypertrophy and 3/4 had an aneurism of the apex. Four out of 5 RA strain inoculated monkeys had an enlarged, flaccid heart; 3/5 aneurism of the apex and 2/5 concentric hypertrophy of the left ventricle.(ABSTRACT TRUNCATED AT 250 WORDS)