To determine the importance of bacteremia in hospitalized patients with diarrhea in Bangladesh, from September 1982 through August 1983 the authors obtained blood for culture from 1,824 patients who were suspected of having sepsis (44% of all admissions). Nontyphoid bacteremia occurred in 243 patients. The most common pathogens were the Enterobacteriaceae (n = 66 episodes), Staphylococcus aureus (n = 65), Pseudomonas aeruginosa and other non-glucose-fermenting bacilli (n = 50), Streptococcus pneumoniae (n = 40), and Haemophilus influenzae (n = 16). When compared with an equal number of control patients without bacteremia, bacteremic patients were significantly (p less than 0.05) more likely to be under 1 year of age (46.5% of bacteremic patients vs. 30.0% of control patients) and more often had abdominal tenderness (20.1% vs. 11.5%), hypoproteinemia (a serum protein level less than 60 g/liter) (58.9% vs. 42.9%), and a prior intravenous infusion (49.0% vs. 30.9%). The case-fatality rate was 29.7% in bacteremic patients versus 7.8% in controls (relative risk (RR) = 3.8, p less than 0.001). Factors that were associated with an increased risk of death in bacteremic patients were infection with a Gram-negative pathogen (RR = 2.48), decreased peristalsis (RR = 2.66), hypoproteinemia (RR = 3.36), hypothermia (RR = 2.54), and hypotension (RR = 2.19). Bacteremia appears to be an important link between diarrheal illness and death in Bangladesh. In children with diarrhea who are suspected of being septic, early implementation of antimicrobial therapy that is effective against the broad range of pathogens identified appears to be indicated.