OBJECTIVE: To evaluate the benefits, risks, and costs of antimicrobial regimens used for selective decontamination of the digestive tract (SDD) in intensive care unit (ICU) patients. DATA SOURCES: Information was obtained from clinical trials, review articles, abstracts, and textbooks. Key indexing terms included antibiotics, selective decontamination, and infections. STUDY SELECTION: Research articles describing controlled clinical trials of SDD in medical or surgical ICU patients were reviewed. Trials that investigated transplant, cirrhotic, leukemic, or oncology patient populations were excluded. DATA EXTRACTION: The details of studies that evaluated nosocomial infection or nosocomial pneumonia rates were extracted. These included study design, demographics, SDD regimens, severity of illness scores, and colonization, infection, and mortality rates. DATA SYNTHESIS: The use of SDD in mechanically ventilated surgical or trauma ICU patients reduces the incidence of colonization, nosocomial pneumonia, and overall infection rates, but does not change the overall mortality rate. Administration of antibiotic and antifungal agents in a nasogastric suspension is required for SDD. The addition of systemic prophylactic antibiotics or oropharyngeal paste was not required to decrease nosocomial infections. The most frequently studied SDD regimen (colistin/amphotericin B/tobramycin) is not feasible for use in the US because of exorbitant drug costs. Less expensive alternatives include norfloxacin/nystatin, or colistin/nystatin/gentamicin. CONCLUSIONS: Additional research is required before SDD regimens can be routinely recommended in surgical and trauma ICU patients. A multicenter study is warranted to determine the long-range benefits, potential for resistance, and cost-effectiveness of SDD.