Because previous attempts to diagnose and quantitate tricuspid regurgitation (TR) by angiography have been unreliable, 60 patients with mitral or combined mitral and aortic valve disease had right ventriculography using a special preshaped catheter. A clinical diagnosis of TR was confirmed in 45% of the patients with moderate and severe TR. A pansystolic murmur increasing in intensity with inspiration, a pulsatile liver, and a prominent CV wave in the jugular veins when present together were specific for severe TR but were seen in only 30% of the patients with severe TR but were seen in only 30% of the patients with severe TR (3+ or 4+). Ventricularization of the right atrial pressure contour was specific for severe TR but was seen in only 40% of the patients with severe TR. A normal right atrial mean pressure (RAP) did not exclude TR, but a rise in RAP or an unchanged RAP with deep inspiration was seen in all patients with TR. Similar findings were observed in two patients with severe pulmonary hypertension who had no TR. There was no relation between the magnitude of this rise in RAP, the degree of pulmonary hypertension, and the severity of TR. The use of a special preshaped catheter tends to avoid the induction of premature beats, and right ventriculograms with a preshaped catheter may be useful in diagnosing TR.