Fifty cases of extensive and necrotizing perineal cellulitis ("perineal gangrene") are reported. The disease, remarkable for its many anatomical and bacteriological varieties, is regarded as a therapeutic requiring multidisciplinary management. Bacteriological samples were polymicrobial in 40 cases. Streptococcus D and aerobic Gram-negative bacilli were isolated in 21 patients. The initial antibiotic treatment had to be modified on ten occasions in 36 patients who were given penicillin G in high doses and on five occasions in 14 patients who received a beta-lactam antibiotic active against anaerobes. Nineteen patients (38 p. 100) died; death was directly related to the sepsis in 16 cases. The death rate was the same in the two treatment groups (11/36 and 5/14) and similar to that found in the literature. The authors advocate an ureidopenicillin, fosfomycin and imidazole combination as a substitute for the conventional penicillin G, aminoglycoside, imidazole combination, since the former is active against Streptococcus D and has better tissue penetration.