A 49-year-old woman had a six-week history of increasing shortness of breath and fatigue. X-ray films and pulmonary scans showed multiple areas of emboli, especially in the right lung. Treatment with heparin was unsuccessful, and although a repeat scan showed only slight changes, the patient's condition deteriorated. Acute pulmonary edema and ventricular tachycardia preceded her death. Autopsy revealed a primary intimal sarcoma with osteogenic elements arising in the posterior leaflet of the pulmonary valve and obstructing the main pulmonary artery and its right branch.