OBJECTIVE Fusobacterium bacteremia is uncommon, accounting for approximately 0.9% of patients with bacteremia. The objectives of this study were to evaluate the incidence and clinical significance of blood cultures positive for Fusobacterium spp., risk factors for mortality, and the impact of antimicrobial therapy on clinical outcomes. METHODS This was a 5-year retrospective study in which the medical records of patients with Fusobacterium bacteremia treated at the Division of Infectious Diseases, Chang Gung Memorial Hospital, Taoyuan, Taiwan, from 2002 to 2006 were analyzed. RESULTS Fusobacterium spp. accounted for 0.74% of 16,676 positive blood cultures. 123 patients were included in the study, 53 of whom had polymicrobial bacteremia (43.1%). Fusobacterium nucleatum was the most common species identified (41.5%). The mean age +/- standard deviation of the patients was 62.6 +/- 18.9 years. The most common sources of bacteremia were the gastrointestinal tract, lower respiratory tract, and skin and soft tissue. Thirty four patients (27.6%) had no definite loci of infection. The overall mortality rate was 40.7% (50 patients), which was not associated with inappropriate empirical antibiotic therapy (p = 0.950), Fusobacterium spp., source of infection, or polymicrobial bacteremia. Shock, lack of fever at presentation, and underlying diseases (heart failure, renal insufficiency, or malignancy) were independent risk factors for mortality. CONCLUSIONS Fusobacterium bacteremia was associated with a high mortality rate for patients with renal insufficiency, heart failure, or malignancy. Delayed start of appropriate antimicrobial therapy did not impact the outcomes.