The results of surgery in a series of 71 patients operated upon for infective endocarditis on a native valve are presented. The patients' mean age was 35 years; the initial focus of infection was usually located in the mouth and the most frequent pathogens were staphylococci and streptococci. The aortic valve was most frequently involved. Only 26 patients underwent surgery after 40 days of antibiotic therapy; 34 were operated upon in a semi-emergency and 11 in an acute emergency. Pre-operative systemic embolism was common (20 cases), notably in the brain (17 cases), and 11 patients remained with sequelae. There was good correlation between the anatomical lesions found at surgery and the data obtained from pre-operative echocardiography. The operation was performed on one valve in 40 cases, on two valves in 20 cases and on three valves in 11 cases. Bioprostheses were used more often than mechanical prostheses. Hospital mortality was nil in patient who underwent elective surgery; it was 14.7 p. 100 in those operated upon in a semi-emergency and 27.3 p. 100 in those operated upon in an acute emergency. Nine patients developed late complications, mostly within 6 months of the operation; in particular, prosthesis disinsertion occurred in 4 cases, and progression of a pre-existing left cardiac failure was observed in 2 cases. In their conclusions the authors emphasize the reliability of echocardiography and the need for an early operation in cases with haemodynamic disorders in order to avoid severe myocardial failure and, if possible, systemic embolism and its fearsome sequelae.