Intra-abdominal sepsis may be caused by intestinal bacteria or by skin bacteria. In the largest series of patients studied in trials of quinolones, anti-anaerobic drugs were included in the therapeutic regimen. Several small series have reported success without the concomitant use of anti-anaerobic drugs. The balance of evidence at present suggests that the quinolones referred to in this report should be supplemented with anti-anaerobic drugs in the treatment of peritonitis related to bowel disease. Quinolones alone have been highly effective in the treatment of peritonitis associated with chronic ambulatory peritoneal dialysis, spontaneous bacterial peritonitis and biliary sepsis. Notwithstanding this success, the potential for an anaerobic aetiology in biliary sepsis and bacteremia must be borne in mind. Lack of clinical efficacy may be associated with resistant bacteria including streptococci. Quinolones offer a relatively non-toxic alternative in the management of intra-abdominal sepsis as well as being cost-saving since early discharge from hospital on oral medication is possible.