Bacteremia with resistant Enterobacter species has been reported in febrile, neutropenic cancer patients receiving beta-lactam antibiotics. To assess the relationship between enterobacter bacteremia and ceftazidime monotherapy, medical records were reviewed and isolates were tested from 16 neutropenic and 35 nonneutropenic patients with Enterobacter bacteremia. Fifteen isolates from the neutropenic patients were resistant to extended spectrum cephalosporins; only 12 of 35 isolates from the nonneutropenic patients were resistant to Enterobacter species. The neutropenic patients also had more beta-lactam therapy, both immediately before bacteremia and in the preceding year, than did nonneutropenic patients. Prior beta-lactam antibiotic exposure may predispose neutropenic patients to develop resistant Enterobacter bacteremia.