The results obtained in a series of 142 patients operated upon, between December 1978 and December 1987, for infective endocarditis on native valve are reported. 61 patients (group 1) had acute progressive endocarditis and 81 patients (group 2) had subacute old-standing endocarditis. In group 1 patients, hospital mortality (i.e. occurring during the first 30 post-operative days) was 11.5 p. 100. During a mean follow-up period of 37.6 months (1.5 to 104.5 months), the survival rates were 52 p. 100 at 72 months and 37.4 p. 100 at 104.5 months. Mechanical desinsertion without persistence or relapse of the infective process, and recurrent endocarditis accounted for 27.8 p. 100 of deaths of known cause. Prognosis was better in group 2 patients. Hospital mortality was 4.9 p. 100, and during a mean follow-up period of 58 months (2 to 124 months) the survival rates were 84 p. 100 at 72 months and 73.4 p. 100 at 124 months. 60 p. 100 of late deaths of known cause were due to heart failure. In native valve infective endocarditis the post-operative diagnosis depends upon the pre-operative haemodynamic status, and the assessment of this status (notably with echocardiography) is a crucial element in the decision to operate.