We present what we believe is the first case in the literature of carcinoma of the lung presenting de novo as an intracardiac mass with bilateral, simultaneous popliteal artery embolization. Arterial thromboembolism of cardiac origin and in situ thrombosis of a preexisting atherosclerotic lesion or aneurysm account for the majority of cases of acute lower extremity ischemia. Less common causes include trauma, aortic dissection, venous ischemia, and foreign body or tissue embolization. Although the history, physical examination, and electrocardiographic findings may provide a likely explanation in many cases, noninvasive studies such as echocardiography may help further elucidate the embolic source.