To avoid the possibility of a fracture of the welded two-armed outflow strut of the Björk-Shiley heart valve, since 1982 it has been machined from one piece of Haynes 25 in the form of a monostrut valve without welds. Of the first 864 patients with a monostrut Björk-Shiley valve implanted, 268 have now been followed up to 3 years. The clinical findings, as well as absence of hemolysis, excellent hemodynamics even with a narrow aortic root as demonstrated by transseptal cardiac catheterization and excellent functional improvement are reported. No valve thrombosis in patients receiving anticoagulant therapy was observed with valves in either the aortic or the mitral position and there was no case of mechanical failure.