Three patients developed acute pulmonary embolism after cerebral angiography. The diagnoses were based on the clinical symptoms and echocardiography, chest roentgenography, blood gas analysis, and pulmonary perfusion scans after intravenous injection of 5 mCi of technetium-99m-labeled human albumin macroaggregates. Two of the three patients achieved clinical improvement, but one patient with severe embolization and circulatory deterioration died in spite of anticoagulation therapy. Recognition of the potential risk of pulmonary embolism after angiography and active prophylaxis are most important in preventing this complication.