A review of 132 consecutive cases of acute pulmonary embolism (PE) documented by pulmonary angiography indicated that syncope was the initial or predominant clinical feature in 17 (13%). When massive PE causes syncope in a nonhospitalized patient, the diagnosis of PE is frequently overlooked. Hypotension after PE may resolve spontaneously after a short interval. In this circumstance, the syncopal episode might easily be attributed to another cause. The appropriate diagnosis can be established only if other clues, suggestive of PE, are sought. Both arterial blood gas determinations and pulmonary scintigraphy are helpful in making this diagnosis.