The Surgical Infection Society last published guidelines on antimicrobial therapy for intra-abdominal infections in 1992 (Bohnen JMA, et al., Arch Surg 1992;127:83-89). Since then, an appreciable body of literature has been published on this subject. Therefore, the Therapeutics Agents Committee of the Society undertook an effort to update the previous guidelines, primarily using data published over the past decade. An additional goal of the Committee was to characterize its recommendations according to contemporary principles of evidence-based medicine. To develop these guidelines, the Committee carried out a systematic search for all English language articles published between 1990 and 2000 related to antimicrobial therapy for intra-abdominal infections. This literature was reviewed individually and collectively by the Committee, and categorized according to the type of study and its quality. Additional articles published prior to 1990 were also utilized when necessary. By a process of iterative consensus, the Committee developed provisional guidelines for antimicrobial therapy for intra-abdominal infections based on this evidence. Following extensive review by members of the Society, these guidelines were approved for publication in final form by the Council of the Surgical Infection Society. This executive summary delineates the Society's current recommendations for antimicrobial therapy of patients with intra-abdominal infections. Topics discussed include the selection of patients needing therapeutic antimicrobials, duration of antimicrobial therapy, acceptable antimicrobial regimens, and identification and treatment of higher-risk patients. Guidelines for patient selection and specific antimicrobial regimens were based on relatively good evidence, but those regarding optimal duration of therapy and treatment of higher-risk patients relied mostly on expert opinion, since there was a paucity of high-quality studies on those issues. Relevant areas for future investigation include the safety, convenience, and cost-effectiveness of available antimicrobial regimens for lower-risk patients, and better means for identifying and treating higher-risk patients with intra-abdominal infections.