AbstractThe Jyros bileaflet mechanical prosthesis is unique among bileaflet valve designs in that there is no fixed hinge mechanism and after implantation, the leaflets are free to rotate as determined by blood flow through the orifice. Between November 1992 and April 1994, 56 Jyros valves were implanted in 44 patients at 45 operations. There were 31 males and 13 females (ratio 2.3:1), with a mean age of 3714 and a range owelve patientsplacement (AVR) (26.7%), 19 had mitral valve replacement (MVR) (42.2%), and 14 had AVR plus MVR (DVR) (31.1%). In three DVR patients the Jyros valve was implanted only in the mitral position. There was one hospital death following DVR (2.3% mortality). Total follow‐up of 341 patient‐months (28.4 patient‐years) is 100% complete. There were no late deaths. There was one reoperation for acute mitral prosthetic thrombosis (3.5%/patient‐year). Another Jyros valve was inserted; leaving 53 valves at risk in 42 patients at the close of follow‐up. There were no episodes of thromboembolism, transient ischemic attacks, endocarditis, hemolysis, or valve dysfunction, but three patients had four episodes of anticoagulant‐related hemorrhage. Echocardiographic follow‐up data was available in 29 patients and indicated satisfactory hemodynamic performance. Our early results with this unique prosthesis have been excellent; however, more extensive use and far longer follow‐up are required to determine whether the theoretical advantages offered by the innovative design are manifest in lower complication rates than for other conventional bileaflet prostheses