Bordetella holmesii is a recently identified gram-negative bacterial species associated with bacteremia, endocarditis, and respiratory illness, mainly in immunocompromised patients. From isolates submitted to the Centers for Disease Control and Prevention from 1983 through 2000 for further identification, we identified 30 patients with B. holmesii bacteremia. Of the 26 patients for whom data were available, 22 (85%) were anatomically or functionally asplenic. In 25 (96%) of the 26 patients, B. holmesii was the only organism isolated from blood samples, and 14 patients (54%) had B. holmesii recovered from > or =2 blood cultures. The clinical course of the infection was generally characterized by a nonspecific febrile illness. Twenty-one patients (81%) were treated with various antimicrobial agents, and 20 (77%) were admitted to the hospital. There were no deaths. Our findings support evidence that B. holmesii may be a true pathogen associated with bacteremia among asplenic patients.