The first case of Thermomyces lanuginosus endocarditis occurring on a porcine heterograft prosthesis, secondary to a Staphylococcus aureus infection of the aortic valve, is reported. The diagnosis was made post-mortem by direct examination of the prosthesis and culture of surgical samples on Sabouraud's agar. Identification was based on the presence of warty, dark brown aleurioconidia. The route of contamination could not be established but the most likely cause was the air of the operating room or the insertion of a contaminated graft.