The hemodynamic changes of the left ventricle (LV) of golden hamsters surviving for 14 months after acute coxsackie B3 virus myocarditis were assessed with the use of a high fidelity micromanometer pressure system. Of 25 infected hamsters, 10 survived to the 14th month, and 4 of these had cardiomegaly. Body weight (BW) was 150.0 +/- 20.7 g (mean +/- SD) (controls, 164.5 +/- 20.1 g, NS); heart weight (HW), 0.499 +/- 0.084 g (controls, 0.448 +/- 0.035 g, NS); and HW/BW, 3.39 +/- 0.79 X 10(-3) (controls, 2.74 +/- 0.23 X 10(-3), p less than 0.05). The hemodynamic data under anesthesia were: HR, 378 +/- 42 (controls, 414 +/- 43, NS); LVSP, 108 +/- 16 mmHg (controls, 126 +/- 16, NS); LVDP, 4.0 +/- 4.8 mmHg (controls, 0.6 +/- 0.7, NS); LVEDP, 9.7 +/- 7.5 mmHg (controls, 3.4 +/- 1.4, NS); peak positive dp/dt, 4960 +/- 1431 mmHg/sec (controls, 6714 +/- 1326, p less than 0.05); (dp/dt)/DP40, 56.8 +/- 9.8 sec-1 (controls, 73.1 +/- 7.0, p less than 0.01); peak negative dp/dt, 3876 +/- 1072 mmHg/sec (controls, 4971 +/- 599, p less than 0.05); and time constant T of LV pressure fall, 7.7 +/- 1.3 msec (controls, 5.9 +/- 0.7, p less than 0.01). Five hamsters had congestion of the lungs and liver with or without an elevation of LVEDP. One of them had an organizing thrombus in the left atrium, and one had an aneurysm in the LV free wall. Though markedly varied in extent, residual myocardial fibrosis was always evident in the hearts in which isovolumic contractility and early diastolic relaxation of the LV were significantly impaired. In a clinical extension of these findings, it may be that some cases of dilated cardiomyopathy in man develop in a way similar to the pathological processes noted in this experiment.