There is little information available on invasive group B Streptococcus (GBS) infection in pediatric patients older than 3 months of age. Review of infection control records at LeBonheur Children's Medical Center from January 1, 1986, to June 30, 1993, identified 143 patients with a positive GBS culture from normally sterile body fluid. Medical records of 18 (13%) patients > 3 months old with their first GBS infection were reviewed. Age range was 15 weeks to 18 years (median age, 13 months). Ten were black and 11 were girls. Five infants had a history of premature birth and 2 infants were infected with human immunodeficiency virus. The serotype distribution of 12 available GBS isolates was 4 type III, 2 each type V and Ia and 1 each type Ia/c, Ib/c, II and II/c. Bacteremia without a focus (9 patients) was the most common clinical manifestation. All 4 type III isolates were associated with bacteremia. One infant with human immunodeficiency virus infection had sepsis and bullous desquamation; a toxin-producing type V strain was isolated from her blood. Two adolescents with ventriculoperitoneal shunts had meningitis, including one whose cerebrospinal fluid also grew a type V strain. Other clinical manifestations were septic arthritis, endocarditis (Ia, II/c), central venous catheter (Ia/c) and ventriculostomy infections.