OBJECTIVE Functional tricuspid regurgitation (TR) is found not infrequently in conjunction with aortic stenosis. The aim of the present study was to evaluate the changes in TR and to identify the predictors of late progression after aortic valve replacement. METHODS We evaluated 354 patients who had undergone aortic valve replacement for aortic stenosis from January 1995 to December 2009. Patients with mitral regurgitation were excluded. Of the 354 patients, 54 had TR greater than mild. The mean follow-up duration was 4.4±4.3 years (maximum, 15). The serial echocardiographic and clinical data were analyzed. RESULTS No early mortality occurred, and the late cardiac mortality rate was 3.9% (14 of 354). In the 48 patients with TR greater than mild, TR did not improve in 23 (49.1%) during the follow-up period. Freedom from cardiac mortality at 10 years was lower in those with TR greater than mild than in patients without TR (61.6%±16.7% vs 93.0%±2.9%, P=.008). Left ventricular diastolic function correlated with right ventricular systolic pressure (P<.001) and the degree of TR during follow-up (P=.001). Multivariate analysis showed that postoperative atrial fibrillation (odds ratio, 6.8; P=.001) and the aortic transprosthetic mean pressure gradient (odds ratio, 1.1; P=.028) predicted late TR greater than mild. CONCLUSIONS Not only did TR in patients with aortic stenosis frequently persist after aortic valve replacement, it was progressive in some. This finding was associated with left ventricular diastolic dysfunction. A concomitant tricuspid valve procedure could be considered in selected patients with aortic stenosis to avoid late TR.