The purpose of this study was to assess the usefulness of two-dimensional echocardiography in the diagnosis of myocardial contusion resulting from blunt chest trauma. In 25 anesthetized dogs, blunt chest trauma was delivered to the right or left chest using a captive bolt pistol. Eighteen dogs survived. Two-dimensional echocardio-graphic recordings and myocardial perfusion determinations (microspheres) were performed before and 15 and 90 minutes after trauma. Pathologic examination confirmed and localized the extent of myocardial contusion. When trauma was delivered to the left side of the chest, two-dimensional echocardiographic and pathologic abnormalities were primarily in the anterolateral wall of the left ventricle; right chest trauma produced septal and right ventricular wall contusion. From short-axis two-dimensional echocardiographic recordings, the end-diastolic wall thickness and systolic function of regions that corresponded to areas of damage in anatomic sections were analyzed and compared with those of remote normal-appearing regions. The contused region showed increased end-diastolic wall thickness and impaired regional systolic function. Further, there was a visible increase in the echo brightness in the contused region. Regional perfusion was norma) and thus the functional impairment of the contused myocardium was not due to ischemia. Other abnormalities observed on the two-dimensional echocardiograms included pericardial effusion and discrete intramyocardial sonolucent zones due to hematomas. Contused myocardium can be identified on a two-dimensional echocardiogram by 1) increased end-diastolic wall thickness, 2) increased echo brightness, and 3) impaired regional systolic function. Two-dimensional echocardiography can also demonstrate other complications of cardiac trauma such as intramyocardial hematoma and hemopericardium.