Two hundred and fourteen episodes of polymicrobial bacteremia in 182 cancer patients in a period of 6 years in a 360-bed National Cancer Institute were analyzed for etiology, risk factors and outcome. Variables were compared with 187 episodes of monomicrobial bacteremias in 147 cancer patients to find statistical significance among risk factors, etiology and outcome. Urinary catheters and breakthrough bacteremia were the only risk factors associated with polymicrobial in comparison to monomicrobial bacteremia (P < 0.05). Concerning etiology, Enterococcus faecalis, Candida spp., Acinetobacter calcoaceticus and Stenotrophomonas maltophilia were more commonly isolated in polymicrobial than in monomicrobial bacteremic episodes. Polymicrobial bacteremia presented more frequently with septic shock (22.9% vs. 9.0%, P < 0.05) and/or organ complications (25.2% vs. 11.8%, P < 0.05). However, mortality due to bacteremia did not significantly differ between polymicrobial and monomicrobial, but when polymicrobial bacteremia with and without coagulase negative staphylococci were compared, mortality in polymicrobial bacteremia without staphylococci was higher (10% vs. 4.7%, P < 0.04).