Until recently intra-abdominal sepsis following surgery for perforated appendicitis has remained a frequent occurrence. In 1975 Fowler reported an incidence of one intra-abdominal abscess in 36 perforated appendicitis treated with a protocol consisting of saline irrigation at surgery, followed by intraperitoneal administration of cephaloridine q. 6 hours for 48 hours. The same antibiotic was then given i.v. for 72 hours. He concluded that this method was an effective way to minimize post-op intra-abdominal abscess, and that the intraperitoneal route was more effective, for this purpose, than systemic administration. More recently, with better knowledge of the role of anaerobes, improved results have also been obtained by adding clindamycin or metronidazole to the antibiotic regimen. A prospective study based on two groups of patients randomly assigned to two protocols was undertaken. The study group consisted of 45 children operated for perforated appendicitis with abscess or generalized peritonitis. These patients were treated with Fowler's protocol. Because it is less nephrotoxic and is active against the same organisms, cefazolin was used instead of cephaloridine. The control group consisted of 43 patients, also operated for perforated appendicitis, treated with saline irrigation at surgery, with either i.v. gentamycin or tobramycin and clindamycin or metronidazole for an average of 7.8 +/- 3.1 days. Both groups were fairly well matched in terms of age, sex, severity of disease, and bacterial flora. They showed an identical 6% post-op intra-abdominal sepsis rate. Days before afebrile, days under gastric suction, complications and average hospital stay were comparable in both groups. The wound infection rate was 20% in the study group and 9% in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)