Two sectional studies about chronic Chagas' disease were performed at a 4.5 year interval, involving the urban populations of Agua Branca, Catingueira, Emas, Imaculada, Mãe D'Agua, Olho D'Agua, Piancó and São José de Caiana counties in the Sertão region of the State of Paraíba. The evolution of heart disease was evaluated in 125 matched pairs of chronic chagasic and non-chagasic patients of the same sex, age and county of origin through electrocardiograms (ECG) at rest. The following evaluation criteria were considered: unchanged - no change in the original ECG pattern; progressive-changes in ECG pattern from normal to abnormal or deterioration of ECG abnormalities; and ECG normalization. In chagasic patients evolution of the disease was unchanged in 101 (80.8%), progressive in 13 (10.4%) and ECG normalization in 11 (8.8%), while those observed in non-chagasic patients were respectively values 117 (93.6%), 6 (4.8%) and 2%) patients. Findings indicate that the share of Chagas-linked etiological component affecting the development of chronic Chagas cardiopathy was 5.9% with an estimated annual average of 1.3%. There was no significant difference in the frequency of progressive disease between the sexes either in the chagasic or in the non-chagasic group. On the other hand, progression of heart disease occurred earlier among chagasic patients. Lethality caused by heart disease was 1.6% (2 cases) in the chagasic group and zero in the non-chagasic group during the period under survey. These morbidity and mortality rates were significantly lower than those found in endemic areas such as Virgem da Lapa and Pains-Iguatama in the State of Minas Gerais and can probably be attributed to the weaker pathogenic it of human infection by Trypanosoma cruzi in the Paraíba hinterland.