A rare cause of pulmonary embolism and pulmonary artery hypertension in young women is choriocarcinoma growing in the pulmonary artery. This growth is reversible, and the disorder can be cured. We describe three patients with this feature who have been treated with appropriate high-risk chemotherapy and who are now in remission. Contrast-enhanced computed tomography can be used to identify major emboli, and progress of the disease can be monitored by serial ventilation/perfusion scans and measurement of serum human chorionic gonadotropin. Recognition of this rare syndrome is important because of the generally excellent outlook with appropriate treatment.