BACKGROUND: Group B streptococci (GBS) are major cause of meningitis and septicemia in neonates and pregnant women, but the importance in non-pregnant adults has not been clearly defined. METHODS: Medical records of all patients with group B streptococcal bacteremia from 1988 to 1997 at Asan Medical Center were reviewed. We compared the clinical and laboratory findings of non-pregnant adults to those of neonates. RESULTS: In a 8-year period there were 41 patients with GBS bacteremia. Thirteen (31.7%) patients were neonates (mean age 14.0+/-11.5 day) and 28 (68.3%) were non-pregnant adults (mean age 52.8+/-13.3 year). Community-acquired infections were 2 cases (15.4%) in the neonates and 7 cases (25.0%) in the non-pregnant adults. In the non-pregnant adults, the most common clinical diagnosis was bacteremia without identified source (15 cases, 53.6%). The others were bone or joint infection (6), urinary tract infection (4), pneumonia (2), skin infection (2), peritonitis (2), and meningitis (1). GBS bacteremia was more common in old age (50 years, 20 cases, 71.4%), the presence of diabetes mellitus (10), solid tumors (10) and liver cirrhosis (10). The mortality rate in non-pregnant adults was 35.7% (10 cases), accounting for 10.7% (3) of deaths related to GBS. In the neonates, early onset infection were 5 cases (38.5%) and late onset infection were 8 (61.5%). The presumed portal of entries were bacteremia without identified focus (5 cases, 38.5%), and meningitis (8, 61.5%). The mortality rate in the neonates was 23.1% (3 cases) and 7.1% (1) related to GBS bacteremia. CONCLUSION: GBS bacteremia is a serious problem not only in the neonates and pregnant women but also in the non-pregnant adults, especially those who are elderly patients with significant underlying diseases.