Aim - to compare long-term results in patients with corrected and uncorrected mild functional tricuspid insufficiency operated for rheumatic mitral defect. Material and methods. It was analyzed treatment of 210 patients with rheumatic mitral defect, functional tricuspid insufficiency degree 1 and 2, moderate dilatation of tricuspid fibrous ring and pulmonary hypertension. 98 (46.7%) patients underwent tricuspid valve annuloplasty in addition to mitral surgery (group 1). Annuloplasty was not performed in 112 (53.3%) patients (group 2). There were statistically significant dilation of left and right cardiac chambers, more severe tricuspid regurgitation (0.9±0.8 and 0.6±0.7; p=0.005), larger diameter of tricuspid fibrous ring (32.9±3 and 31.2±2.7; p<0.001, 95% CI 1-2.5), more severe pulmonary hypertension (44,6±9,4 and 40±10; p=0.001, 95% CI 1,9-7.2) with normal left ventricular contractility (56.3±10,5 and 61.2±9.9; p=0.001, 95% CI 2.1-7.7) in group 1. Results. There were no early postoperative deaths in both groups. In group 1 tricuspid regurgitation decreased from 0.9±0.8 to 0.2±0.4 (p<0.001), in group 2 - from 0.6±0.7 to 0.1±0.4 (p<0.001). Statistically significant difference was absent between groups (p=0.072). Postoperative complications were observed in 10 (10.2%) and 12 (10.7%) patients in both groups respectively. Long-term results were assessed in 195 (93%) patients during 7.6±3.5 years (0.1-14.4). Complications in long-term period occurred in 33 and 26% in both groups respectively (p=0.344). 10- and 14-year survival was 74.5±7.2 and 61.5±10.3% in group 1 respectively. The same parameters were 74.4±5.3 and 65.8±6.6% in group 2 (p=0.715). 10- and 14-year freedom from cardiovascular complications was 76.9±5.0 and 53.9±11.8% in group 1 respectively. In group 2 the same values were 70.8±5.7 and 55.8±8.1% respectively (p=0.707). Long-term NYHA functional class was 2.3±0.7 and 2.3±0.6 in groups 1 and 2 respectively (p=0.751, 95% CI 0,3-0,2). Dynamics of tricuspid regurgitation in group 1 - 0.9±0,8 before surgery, 0.2±0.4 after surgery and 0.6±0.7 in remote period (p<0.001), in group 2 - 0.6±0.7 before surgery, 0.1±0.4 after surgery and 1.3±0.9 in remote period (p<0.001). Conclusion. Surgical correction of mild functional tricuspid insufficiency in patients with moderate dilatation of the fibrous ring and pulmonary hypertension operated for rheumatic mitral defect does not improve the prognosis and is not advisable.