Capnocytophaga spp. are thin, spindle-shaped, gram-negative bacilli, similar to fusobacteria. We isolated Capnocytophaga from the blood of three patients with fever: two acute myelogenous leukemia patients and one chronic osteomyelitis patient. The patients showed mild course of disease without hypotension or the change of mental status. As Capnocytophaga spp. are slow growing bacteria, there were difficulties in the isolation and susceptibility test of bacteria. More concerns should be given to the uncommonly isolated bacteria such as Capnocytophaga.