SummaryAt the present time the choice in prophylaxis is determined by bactériologie trends and data. It can be summarised as follows :1) no blind prophylaxis : its effectiveness is nil;2) semi-specific prophylaxis of bacterial endocarditis in function of the injured organ and of its flora : penicillin-streptomycin (buccal cavity), ampicillin-kanamycin (urinary, bilary, genital and digestive tracts); duration : 72 hours; frequent successes;3) specific anti-streptococcal prophylaxis of the rheumatic fever and its relapses : penicillins; indications beyond discussion; success guaranteed.New oral penicillins, lincomycin. oxacillin and gentamicin are indicated respectively in the prevention of rheumatic fever in cooperative patients, in the treatment of streptococcal pharyngitis, in heart surgery and in infections caused by resistant Gram negative micro-organisms.