Three hundred and seventy eight patients with infectious endocarditis (IE) were studied, including 299 cases of native IE [154 subacute (SIE), 145 acute (AIE)] and 79 cases of prosthetic endocarditis (PIE). One hundred and fifty patients were operated on (40%): 117 for haemodynamic complications, 10 for bacteriological indications and 23 for mixed indications (112 patients in the acute phase). Complications were more frequent in AIE than in SIE, in PIE than in native IE. Surgery is more urgent in aortic insufficiency and in Oslerian mitral stenosis (7 cases) than in mitral insufficiency. Eight tricuspid valvulectomies were performed. In 5 cases out of 11 rupture syndrome was cured without surgery. The patient's clinical condition contra-indicated surgery in 63 cases. The surgical mortality was 51/150 (34%). It was significantly lower in SIE (21%) than in AIE (39%), in native IE than in PIE (53%), after antibiotic therapy than in the acute phase. Mortality was not higher when surgery was performed before the 8th day of antibiotherapy but perivalvular leaks were more common (31% vs 4%, P less than 0.01). Mortality was higher when the culture of valve was positive than when it was negative (45% vs 26%, P less than 0.06). However, surgery should be immediately considered in cases of haemodynamic complications.