Tricuspid regurgitation severity was assessed preoperatively with Doppler color flow mapping and these assessments were compared with surgical findings in 90 patients undergoing mitral or aortic valve replacement, or both. Group I (n = 52) required tricuspid valve annuloplasty because tricuspid regurgitation was judged intraoperatively to be severe; in Group II (n = 38), tricuspid valve annuloplasty was not performed because tricuspid regurgitation was judged intraoperatively not to be severe. With use of the apical four chamber and parasternal short-axis imaging planes, the severity of tricuspid regurgitation by Doppler color flow mapping was assessed by comparing the maximal area of tricuspid regurgitant signals with the right atrial area taken in the same frame in which the maximal tricuspid regurgitant signals were noted. This ratio was found to be ≥34% (mean 50.2 ± 11.8%) in 50 (96%) of 52 patients in Group I and <34% (mean 27.5 ± 6.9%) in 36 (95%) of 38 patients in Group II (p < 0.001). The maximal diastolic tricuspid anulus diameter measured with the same two-dimensional imaging planes was ≥21 mm/m2 body surface area (mean 26.7 ± 5.2 mm/m2) in 46 patients (88%) in Group I and <21 mm/m2 (mean 17.8 ± 2.5 mm/m2) in 36 patients (95%) in Group II (p < 0.001). The percent shortening of the tricuspid anulus diameter was <25% (mean 17.2 ± 6.5%) in 47 patients (90%) in Group I and was ≥25% (mean 31.2 ± 5.9%) in 37 patients (97%) (p < 0.001) in Group II. The two patients groups could not be distinguished with use of two-dimensional right ventricular ejection fraction. Both Doppler color flow mapping and two-dimensional echocardiography are useful in identifying patients who would require tricuspid valve repair for severe tricuspid regurgitation during mitral or aortic valve replacement, or both. © 1989.