Introduction and objectives. To determine the characteristics of Propionibacterium acnes prosthetic valve endocarditis (PAPVE). Methods. Prospective descriptive study of 16 consecutive cases of PAPVE. Results. Seven patients developed PAPVE early and 9 developed it late. In all those who developed PAPVE late, there was a history of mucocutaneous barrier manipulation. The delay in diagnosis was >3 months in 75%. The clinical presentation was asymptomatic prosthetic valve dysfunction in 31%, heart failure in 19%, coronary syndrome in 12.5%, fever in 25%, and neurological deficits in 19%. At diagnosis, 62.5% had heart failure and 44% had fever. The predominant echocardiographic finding was prosthesis dysfunction due to dehiscence of metallic aortic valves (6 out of 7) or stenosis of metallic mitral valves (4 out of 7). In 2 of the 3 biological aortic prostheses, dysfunction was due to leaflet distortion. Blood cultures and surgical specimens tested positive after a mean of 11.6 and 12.2 days, respectively. In 2 cases, the diagnosis was confirmed by PCR. The principle intraoperative finding was the presence of abundant grayish pannus. Histology demonstrated the absence of acute inflammatory features. Twelve patients received antibiotic treatment with valve replacement: 7 were cured, 4 experienced early prosthesis dehiscence and 1 relapsed. All 3 patients who were initially treated with antibiotics alone suffered relapses. Conclusions. Generally, PAPVE presents as prosthetic valve dysfunction with few symptoms of infection. Prolonged incubation of cultures is essential for diagnosis. Antibiotic treatment provides clinical control but does not eradicate the infection, and valve replacement is necessary for a cure. The postoperative course can be complicated by prosthesis dehiscence.