Background.The epidemiology of early onset neonatal group B streptococcal (GBS) disease has changed appreciably, but there are no recent assessments of the in-hospital resource utilization it incurs.Study design.We performed a retrospective cohort study of infants delivered from 1987 through 1995 at Massachusetts' largest obstetrics hospital. A matched cohort design was used to assess care occurring after transfer to another acute care hospital.Results.There were 135 cases of early onset neonatal GBS infection complicating 85 062 deliveries (1.6/1 000 births) in 9 years, with a substantial decline beginning in 1994, when maternal intrapartum chemoprophylaxis was widely introduced. Most (73%) infants had birth weights of 2500 g or more; 93% survived. Overall both the median and mean lengths of stay were 8 days longer for infants with GBS disease than for those without this infection (P< 0.001). Total hospital charges for neonates with GBS disease also were higher, with the difference in medians of $5323 and in means of $10 004 (P< 0.001). Differences were greatest among >2500-g birth weight infants; no excess was evident for infants with birth weights of <1500 g.Conclusion.There was a substantial excess length of stay and charges associated with early onset neonatal GBS disease, although this was less than previously reported.