Although Leuconostoc species with intrinsic high-level vancomycin resistance have rarely been isolated from clinical specimens, this organism may cause serious invasive infections such as bacteremia and meningitis in immunocompromised hosts or patients with a wide spectrum of underlying diseases including alcoholic liver diseases and gastrointestinal diseases. Predisposing factors of Leuconostoc bacteremia include intravenous or enteral feeding catheters, other invasive access devices such as tracheostomy, gastrostomy or endotracheal tubes, and previous antimicrobial treatment. This low prevalence may be due, in part, to the inability of automated systems to recognize this organism. It is important that all Leuconostoc isolates obtained from clinical specimens that are related to serious infections should be identified to species level for appropriate antibiotic therapy. We report two cases of Leuconostoc bacteremia occurring in a 65-year-old male with variceal bleeding, and in a 5 month child with ileostomy receiving total parenteral nutrition therapy. (Korean J Clin Microbiol 2002;5(1):62-67)