Little information is available concerning the relationship between the pattern of the jugular phlebogram and interventricular septal motion. We studied 250 patients with various conditons. Abnormal septal motion was observed in only 33% of the patients with tricuspid regurgitation. All the patients having abnormal septal motion and 66% of those having normal septal motion had the jugular pattern of tricuspid regurgitation. After cardiac operation with the incision of cardiac chambers and pericardiotomy, abnormal septal motion was seen from 40 to 89% at early postoperative period. Of the patients studied approximately 1 year after operation, there was reduced incidence of septal abnormality. Septal motion was normal in all the patients who had ligation of a patent ductus arteriosus and who underwent Blalock's operation. Of these, all having paradoxical motion which occurred in the mid-septum at least had the jugular pattern of tricuspid regurgitation. On the other hand, only 20 to 30% of the patients whose septal motion was normal had the jugular pattern of tricuspid regurgitation. Furthermore, all of the 3 patients with coronary artery disease having paradoxical motion of the entire septum had the jugular pattern of tricuspid regurgitation, as well. We conclude that the jugular pattern of tricuspid regurgitation and echocardiographic septal motion abnormality are related to each other and that tricuspid regurgitation should not be diagnosed by jugular phlebogram unless echocardiographic septal motion is examined.