To determine the frequency and etiology of elevations of CK-MB in patients with pulmonary emboli, we studied 52 patients with well-documented emboli and the absence of known ischemic heart disease or ECG changes suggestive of acute infarction. All patients were evaluated with serial CK-MB determinations at 8-h intervals. All patients with elevations of CK-MB had noninvasive cardiac evaluations. Four (7.7 percent) of the 52 patients had a rising and falling pattern of CK-MB that satisfied enzyme criteria of acute infarction. Three of these four also manifested classic echocardiographic features of right ventricular infarction. None of the four had evidence of left ventricular regional wall motion abnormalities or dysfunction. Of the 48 patients without elevations of CK-MB, only two had segmental right ventricular dysfunction. These findings suggest that pulmonary emboli can induce right ventricular infarction in some (7.7 percent) patients even when patients with a history of coronary artery disease and/or ECG changes of infarction are excluded. Conversely, the diagnosis of pulmonary embolism should be considered in patients when right ventricular infarction is diagnosed.