During a six-year period 23 patients with isolation of Corynebacterium jeikeium (formerly known as Corynebacterium group JK) from one or more blood cultures at a university hospital were identified. Cases occurred sporadically without time- or ward-related clustering. Review of the cases showed that most infections were nosocomial, that most of the patients had underlying malignant disease, had a chronic intravascular catheter implanted, had been pretreated with antibiotics, and were neutropenic at the time the blood cultures were drawn. Patients with only one versus those with more than one positive blood culture differed in some important aspects. Patients with only one positive blood culture were less likely to have acute leukemia, had significantly higher neutrophil counts and a shorter duration of preceding antibiotic treatment, and all had other probable causes of infection and fever. The mortality also appeared to be lower in these patients. Despite the possibility of increasing frequency of blood cultures positive for C. jeikeium, severe infections due to this organism continue to be largely confined to neutropenic patients with hematologic malignancy.