From 1991 to 2000, 125 sporadic cases of Klebsiella oxytoca bacteremia were analyzed retrospectively to review clinical features and to identify the risk factors associated with resistance to extended-spectrum cephalosporins and fatal outcome. Bacteremia was acquired nosocomially in 52% of the patients. Almost all patients (97%) had an underlying disease, with biliary and pancreatic disease occurring most frequently (55%). The biliary tract was the most common site of infection (44%). Resistance to extended-spectrum cephalosporins was identified in 22 of the 125 (18%) Klebsiella oxytoca blood isolates and resistance to ciprofloxacin in 9 (7%). Only previous antibiotic therapy was strongly associated with resistance to extended-spectrum cephalosporins in patients with Klebsiella oxytoca bacteremia ( P=0.009). The mortality rate was 24% and was higher in patients infected with isolates resistant to extended-spectrum cephalosporins (41% vs. 20%; P=0.04). In multivariate analysis, fatal outcome was independently associated with septic shock, deteriorated mental status, polymicrobial bacteremia, and solid tumor. Surgical therapy had a protective effect (OR, 0.06; 95% CI, 0.005-0.7; P=0.03). In conclusion, Klebsiella oxytoca bacteremia was most commonly associated with biliary tract infection. Previous antibiotic therapy was strongly associated with resistance to extended-spectrum cephalosporins in patients with Klebsiella oxytoca bacteremia.