During a five-year period, 204 patients had klebsiella bacteremia at this institution; these cases constituted 6.6% of the total episodes of bacteremia. The incidence was 2.3 cases per 1,000 admitted patients. A random group of 100 cases was chosen for analysis in the present study. The disease was community acquired in 23%, nosocomially acquired in 77%, unimicrobial in 88%, or part of a polymicrobial bacteremia in 12% of episodes. Three-quarters of the episodes were caused by Klebsiella pneumoniae and the remaining one-quarter, by Klebsiella oxytoca. Portals of entry, in decreasing order of frequency, were urinary, respiratory, and biliary tracts. Twenty-four percent of the Klebsiella isolates were resistant to gentamicin. The most frequent clinical finding (in 96% of the cases) was fever. Shock occurred in 22% and pyogenic metastatic foci, in 5% of the patients. None of the patients had evidence of disseminated intravascular coagulation. Overall mortality was 25%, and factors associated with poor prognosis were inadequacy of antimicrobial chemotherapy, septic shock, type of underlying disease, and clinical condition of the patients.