The decision regarding the appropriate empirical antibiotic therapy for bacteremia in patients with hematologic malignancies must be individualized in each institution, by taking into account variations in the patterns of microbial isolates and their resistance profiles. Microbial isolates and antibiotic resistance patterns must be taken into account at each hospital. A shift from bacteremia due to infections caused by predominantly gram-negative organisms to predominantly gram-positive organisms in patients with hematologic malignancies has been noted in reports from other countries. We investigated bacterial isolates and their antibiotic sensitivities in patients with hematologic malignancies in the Veterans General Hospital-Taipei. A total of 185 episodes of bacteremia in 140 patients with hematologic malignancies were recorded during the period from 1995 to 1996. Unlike foreign reports, our investigation shows that gram-negative organisms still predominate, accounting for 72.7% of isolates, followed by gram-positive organisms, accounting for 26.3% of isolates, and anaerobes, accounting for 1% of isolates. Escherichia coli was the most commonly isolated organism, accounting for 23.9% of isolates, followed by Klebsiella pneumoniae (18.5%), Pseudomonas aeruginosa (12.2%), Enterobacter cloacae (7.3%), and methicillin-resistant Staphylococcus aureus (7.3%). A high mortality rate was observed in gram-negative bacteremia: 31% for E. coli, 26% for K. pneumoniae, 24% for P. aeruginosa, and 33% for E. cloacae. If methicillin-resistant S. aureus bacteremia occurred, mortality was high (47%). The antibiotic sensitivity profiles of the four most common gram-negative isolates (E. coli, K. pneumoniae, P. aeruginosa, and E. cloacae) indicated that, in our hospital, amikacin with either cefoperazone, ceftazidime, ciprofloxacin, or imipenem, would be an ideal combination for empirical therapy for bacteremia in patients with hematologic malignancies.