To assess tricuspid regurgitation (TR) in patients with permanent transvenous right ventricular (RV) pacing, we performed phonocardiographic, contrast and pulsed Doppler echocardiographic studies in 18 patients with transvenous leads for RV pacing. In addition, a pathological study was performed on 26 autopsy cases with transvenous leads for RV pacing. None of the patients had right-sided heart failure. The previous phonocardiograms revealed regurgitant murmurs of TR in one clinical case and five autopsy cases. In the clinical study, definite TR was diagnosed both by contrast and pulsed Doppler echocardiography in five cases (28%). Probable TR was diagnosed only by one technique in three cases (17%), and the absence of TR was confirmed by both techniques in 10 cases (55%) (non-TR group). The average right atrial dimension was 59 +/- 5.3 mm in the definite TR group and 39 +/- 2.4 mm in the non-TR group (p less than 0.01). The average inferior vena cava dimension was 19 +/- 1.7 mm in the definite TR group and 15 +/- 0.8 mm in the non-TR group (p less than 0.05). Right atrial and inferior vena cava dimensions showed a significantly positive correlation (r = 0.58, p less than 0.05). In the pathological study, the presence of TR, which was explained by the position of the pacemaker lead in relation to the valve structure, was confirmed in 11 cases (42%). Valve motion interference was classified as type I (two cases), in which the lead was suppressed and the leaflet immobilized, type II (4 cases), in which chordae tendineae were involved by a pacemaker lead, and type III (five cases), in which both mechanisms contributed to valvular regurgitation. In conclusion, TR may follow transvenous RV pacing in approximately half of the cases with RV pacing. Contrast and pulsed Doppler echocardiography are sensitive noninvasive techniques for detecting this valvular abnormality and they should be used in the follow-up of such pacemaker recipients.