The Edwards MC³ tricuspid annuloplasty system has recently become available commercially. Its anatomically correct design conforms to the three-dimensional tricuspid orifice and minimizes stress on sutures. We handled 71 patients with functional tricuspid regurgitation by open heart surgery and tricuspid valve repair between May 2005 and April 2007 in our institute. Cosgrove-Edwards annuloplasty rings were used for tricuspid regurgitation in 33 patients before October 2006. Among them, there were 30 mitral valve surgeries, 6 aortic valve surgeries, and 2 cases of atrial septal defect. Since then, we used the MC³ system in 38 cases, consisting of 30 mitral valve surgeries, 9 aortic valve surgeries, and 2 cases of atrial septal defect. Three patients died postoperatively with the Cosgrove-Edwards system, but there was no fatality with the MC³ system. The degree of tricuspid regurgitation was reduced from 2.6±0.58 to 0.34±0.46 (regurgitation severity scale: 0 to 4) in the patients with the MC³ ring at discharge. In the 33 patients with the Cosgrove-Edwards ring, it was from 2.8±0.67 to 0.92±0.99. The severity of tricuspid regurgitation in patients with the Cosgrove-Edwards ring and the MC³ ring about nine months postoperative was 1.5±1.2 and 0.42±0.50, respectively. The MC³ (rigid ring) system was more effective than the Cosgrove-Edwards (flexible band) system for decreasing tricuspid regurgitation in immediate and short-term postoperative periods.