On May 3, 1962, surgeons performed what is widely regarded as the first successful replacement of a human heart valve using a prosthetic device. The operation took place during a period of rapid innovation in cardiac surgery: open-heart techniques, cardiopulmonary bypass, and early mechanical valve designs had converged to make valve replacement feasible for the first time. Background Diseases of the heart valves—most commonly rheumatic, degenerative, or congenital lesions—had long been major causes of illness and death. Early 20th-century treatments were limited to palliative measures or, later, closed surgical procedures that could not fully correct many valve defects. The development of reliable cardiopulmonary bypass machines after World War II enabled surgeons to stop the heart and operate directly on internal cardiac structures, creating the conditions necessary for valve repair and replacement. The operation and device The 1962 procedure involved excision of the diseased valve and implantation of a mechanical prosthesis designed to replicate unidirectional blood flow. Early prosthetic valves came in several varieties—ball-and-cage, tilting-disk, and bileaflet designs—and materials and geometries were rapidly iterated as surgeons and engineers sought durable, biocompatible solutions that minimized clotting and structural failure. Outcomes and significance The patient undergoing the May 3, 1962 procedure survived and experienced a functional improvement that established prosthetic valve replacement as a viable therapeutic option. That success paved the way for broader adoption of valve replacement surgery during the 1960s and 1970s and spurred further refinements in valve design, anticoagulation management, and perioperative care. Over subsequent decades, mechanical valves were complemented by tissue (bioprosthetic) valves derived from animal tissue or homografts, providing additional options tailored to patient age, comorbidity, and lifestyle considerations. Historical context and limitations Attributing a single ‘‘first’’ in surgical history can be complex. Prior attempts at valve replacement and various experimental implants occurred before 1962, and different teams reported successes with different prosthesis types around the same period. Sources commonly cite the early 1960s as the decisive interval when valve replacement transitioned from experimental to reproducibly successful. Contemporary reports and later historical reviews emphasize that the achievement reflected multidisciplinary advances—in surgical technique, perfusion technology, materials science, and postoperative care—rather than a lone breakthrough. Legacy The successful valve replacement of May 3, 1962 is remembered as a landmark that transformed the treatment of valvular heart disease. It contributed to the expansion of cardiac surgery into a discipline capable of correcting previously fatal structural heart problems, and its legacy includes ongoing innovation in prosthetic design, minimally invasive and transcatheter valve therapies developed decades later, and improved long-term survival and quality of life for many patients worldwide. Sources and verification This summary synthesizes widely reported historical facts about early heart valve replacement in the early 1960s and the broader trajectory of cardiac surgery. Specific institutional records, contemporaneous surgical reports, and later historical reviews provide the primary basis for dating and evaluating these developments; where accounts differ on precise ‘‘firsts,’’ historians typically locate the watershed moment for routine success in the early 1960s rather than a single inventor or center.