We compared the clinical, electrocardiographic and echocardiographic findings of 32 patients during the acute and recuperative phases of viral illness with similar data from a healthy age- and sex-matched normal control group. During the acute phase, no patient had cardiac symptoms and none had clinical evidence of left ventricular or valvular dysfunction, nor pericarditis. Electrocardiograms revealed no differences in mean sinus rate or ectopic dysrhythm between the two groups. Spatial 12- and 120-lead body surface electrocardiographic patterns were normal in 30 patients; two others had nonspecific T wave abnormalities. There were no differences in echo-determined left ventricular cavity size or systolic shortening fraction between the two groups. Three patients had segmental ventricular hypokinesis; 17 patients had small pericardial effusions. Data herein suggest effects on myocardial electrical and mechanical function in patients with viral illness. It may be prudent for such patients to minimize cardiac stress during illness.