The aims of this prospective study were to: (1) determine the rate of blood culture contamination; (2) describe and compare the epidemiologic, clinical and microbiological characteristics of hospital- and community-acquired bloodstream infections; and (3) determine the mortality resulting from bloodstream infections. The rate of true bacteremia was 12.1%, and 10.7% of cultures were contaminated. Of the 567 episodes of bloodstream infection, 73.4% were hospital-acquired, and 26.6% were community-acquired. The most commonly isolated microorganisms were staphylococci (44%, methicillin resistant 69.4%), enterococci (15%) and Escherichia coli (12.5%) in hospital-acquired episodes, and Brucella spp. (21.9%), E. coli (19.2%) and Staphylococcus aureus (14.6%, methicillin resistant 9.1%) in community-acquired episodes. While the overall mortality rate was 25.4%, death attributable to bloodstream infections was 16.6% in hospital-acquired episodes and 13.9% in community-acquired episodes. The highest mortality occurred in patients with bacteremia due to Pseudomonas aeruginosa (37.5%) in hospital-acquired episodes, and in patients with bacteremia due to Streptococcus pneumoniae (50%) in community-acquired episodes. Underlying diseases, severity of illness, presence of bladder catheter, previous use of antibiotics, tracheal intubation and adequacy of treatment were found to be significantly associated with death.