The records of 63 surgical patients with one or more positive blood cultures for Enterobacter organisms were reviewed to determine clinical, epidemiologic, and mortality risk factors. Enterobacter bacteremia occurred, on the average, on the twenty-third day of hospitalization, most frequently in male patients (47), after antibiotic therapy (48 patients), placement of central venous catheters (38 patients), gastrointestinal tract operations (36 patients), and respiratory failure (31 patients). Portals of entry were most commonly sputum (25 patients), open skin wounds (16 patients), and central venous lines (12 patients). Mortality risk (22 patients, 35%) was increased with Enterobacter bacteremia occurring after the fifteenth day of hospitalization (18 of 45 patients versus 4 of 28 patients, p less than 0.01), a preceding Enterobacter focus (13 of 22 patients versus 9 of 41 patients, p less than 0.05), preceding non-Enterobacter bacteremia (10 of 15 patients versus 12 of 48 patients, p less than 0.02), preceding total parenteral nutrition (11 of 21 patients versus 11 of 42 patients p less than 0.01), respiratory failure (19 of 36 patients versus 3 of 27 patients p less than 0.01), and renal failure (11 of 12 patients versus 11 of 51 patients p less than 0.01). The mortality risk was not diminished by specific antibiotic therapy. Enterobacter is emerging as an important pathogen in surgical patients. Prolonged antibiotic administration, particularly that of cephalosporins, may promote Enterobacter colonization of the tracheobronchial tree and skin with subsequent invasion enhanced by respiratory failure, open skin wounds, or central venous catheters traversing the skin. Mortality risk is determined primarily by factors associated with critical illness rather than effects of Enterobacter organisms and their specific treatment.(ABSTRACT TRUNCATED AT 250 WORDS)