This study was based on the analysis of 41 cases of infectious endocarditis of native valves operated during the acute phase. Patients with bacteriological cures, prosthetic valve endocarditis and endocarditis on congenital non-valvular lesions were excluded. There were 32 men and 9 women with an average age of 49 years. The valve lesions were aortic incompetence, mitral incompetence, mitro-aortic disease and mitro-tricuspid disease. Fourteen patients had preexisting valvular disease (rhumatic in 12 and congenital in 2 cases). These patients were in an advanced clinical state at the time of operation: 23 Class IV, 16 Class III and 2 Class II operated for systemic embolism. The surgical indications were severe cardiac failure in 30 cases, systemic embolism in 2 cases and persistance of septicaemia with worsening cardiac function in 9 cases. The causal organism was isolated from blood cultures in 34 cases (83%) and from the excised valve in 13 cases. The early postoperative mortality during the first month was 5 patients (3 cases of aortic incompetence associated with mitral incompetence and 2 cases of aortic incompetence alone). Death was caused in most cases by irreversible cardiac failure related to the advanced preoperative cardiac failure. All the other patients were followed up for 1 to 102 months (average 44 months). There were 7 late postoperative deaths. The mortality rate was 3.4% per patient year including patients undergoing chronic haemodialysis. The actuarial survival was 79% at 78 months excluding the operative mortality.(ABSTRACT TRUNCATED AT 250 WORDS)