We studied the epidemiology, microbiology, clinical presentation and outcome of nosocomial bloodstream infections (NBI) in children and adolescents in southern Israel during 1992-2001. Information on NBI was collected prospectively by active surveillance. NBI was diagnosed when a clinically significant positive blood culture was drawn in a patient during >48 h after admission. 469 episodes occurred in 370 children and adolescents aged 1 m-18 y. The overall incidence of NBI was 5.3/1000 patients, with no increase during the study period. A significant decrease in NBI incidence was recorded at the neonatal intensive care unit (NICU) during 1997-2001 vs 1992-1996. The incidences of NBI at the paediatric ICU (PICU), paediatric wards and paediatric surgery departments (PSD) were 24.1, 2.8 and 2.5/1000 patients, with an increase in NBI cases at PICU and PSD during 1997-2001 vs 1992-1996. Of 661 pathogens, Gram-negative, Gram-positive and fungal organisms were isolated in 54.3%, 36.6% and 9.1% of cases, respectively. Enterobacteriaceae (34.6% of all isolates) were the most frequently isolated Gram-negative organisms. Enterococcus spp., coagulase-negative staphylococci and Staphylococcus aureus (9.5% of all isolates each) were the most frequently isolated Gram-positive organisms. A significant increase was recorded in the incidence of NBI caused by Streptococcus pneumoniae and Pseudomonas spp. A significant decrease in the susceptibility of Enterobacteriaceae spp. to piperacillin, ceftazidime, gentamicin and ceftriaxone was recorded during the study period. 33 (8.9%) patients with NBI died.