The Hall-Kaster pivotal disc prosthetic heart valve was introduced in 1977. The primary goal of the design was to obtain the least possible obstruction to flow. Toward this end, innovations in the tilting axis, disc guidance mechanisms, and disc translational freedom combine to improve flow through both orifice segments of the open valve. The present study reports the primary clinical and hemodynamic findings in 28 patients (mean age, 53.8 years) with aortic valve disease, examined 3 months after insertion of the Hall-Kaster pivotal disc valve. The hemodynamics findings displayed low gradients and high calculated orifice areas. Satisfactory flow was observed through both the major and minor openings of the prosthesis. There were no arterial thromboembolic episodes. The increase in serum lactate dehydrogenase activity was moderate, indicating a slight-to-moderate intravascular haemolysis.