Background This study evaluated the usefulness of 3-dimensional echocardiography (3-DE) for identifying permanent pacemaker (PPM) or implantable cardioverter defibrillator (ICD) lead-related symptomatic tricuspid regurgitation (TR). Methods and Results Eighty-seven patients underwent 3-DE examination: 50 patients with PPM, 17 with ICD, and 20 with cardiac resynchronization therapy devices. TR severity was classified as trivial/mild, moderate, or severe according to the ratio of TR area to right atrium area. The 3-DE identified the lead route and position at the tricuspid valve in 82 patients (94.2%). In 5 patients, images without lead-induced artifacts could not be obtained. TR severity was trivial/mild in 50 patients, moderate in 20 patients, and severe in 12 patients. In all patients with trivial/mild TR and all but 1 patient with moderate TR, leads were positioned on the annulus side between leaflets. Lead-induced obstruction to tricuspid valve closing was identified in 1 patient with moderate TR and in 7 of 12 patients with severe TR: 4 patients had septal leaflet obstruction, and 4 had posterior leaflet obstruction. Conclusions The 3-DE can identify the lead route and position at the tricuspid valve and lead-related severe TR, so may be a useful technique of diagnosing the cause of severe TR in patients with PPM or ICD. (Circ J 2008; 72: 1465 - 1470)