Blood samples, which were obtained from patients who lived in a rural area with approximately 500 acute-care hospital beds, were cultured from 1990 through 1997. We retrospectively reviewed the blood cultures that yielded Clostridium species (74 [0.12%] of 63,296 cultures). These were obtained from 46 different hospitalized patients (incidents per hospital, 0.03%). The source of the Clostridium species was a gastrointestinal site in 24 patients (52.2%). The most frequently identified Clostridium species was Clostridium perfringens (in 10 [21.7%] of patients), followed by Clostridium septicum (in 9 [19.6%]). Thirty-one patients (67.4%) were aged > or =65 years, 13 patients (28.3%) had diabetes mellitus, and underlying malignancy was present in 22 patients (47.8%). The mortality rate of patients whose condition had been managed surgically was 33%; for those patients whose conditions required medical management, the mortality rate was 58%. Clostridium bacteremia in these patients usually had a gastrointestinal source, it often occurred in patients with serious underlying medical conditions, and it rarely was the result of traumatic farm accidents.