Intracardiac phonocardiograms were obtained from the right atrium in order to study the relation between the clinical signs of tricuspid regurgitation, intracardiac murmurs and the degree of regurgitation demonstrated on right ventriculography with use of a preshaped catheter. In five patients with no heart disease, right ventriculograms showed no evidence of tricuspid regurgitation and intracardiac phonocardiograms in the right atrium demonstrated no murmur. Among 35 patients with valvular heart disease, a Carvallo sign (increased intensity of systolic murmur during inspiration) was present in 19 and absent in 16. All 19 patients with a Carvallo sign had variable degrees of tricuspid regurgitation on right ventriculography, and intracardiac phonocardiograms were positive for tricuspid regurgitation in 18. Among 16 patients with an absent Carvallo sign, neither right ventriculography nor intracardiac phonocardiography was indicative of tricuspid regurgitation in 5. Five patients had 1+ regurgitation and the intracardiac phonocardiogram was positive in three of these five patients. The other six patients showed 3+ to 4+ regurgitation and the intracardiac phonocardiogram was positive for tricuspid regurgitation in all. In conclusion, (1) the Carvallo sign is a reliable indicator of tricuspid regurgitation but its absence does not rule it out, and (2) right ventriculography using a preshaped catheter and intracardiac phonocardiography are useful in detecting clinically unrecognized tricuspid regurgitation.