OBJECTIVE: To determine the most frequent bacteria causing infection in hospitalized newborns, and their antimicrobial sensitivity. MATERIAL AND METHODS: Review of the clinical files of Neonatology Division, Children’s Health Institute (Lima, Peru) and identification of the positive cultures and antibiograms from June 1999 until May 2002. RESULTS: During this three year period there were 94 patients with confirmed sepsis from whom 161 samples were obtained (blood, urine, IV catheters, and others ). The most frequently isolated bacteria were: Staphylococcus epidermidis (38,3%), Staphylococcus aureus (12%), Klebsiella sp (10%), Alcaligenes fecalis (4,6%), Acinetobacter sp (4%) and Pseudomonas aeruginosa (4%). S. epidermidis showed 100% sensitivity to vancomycin, 90% to cefotaxime, 50% to amikacin and ampicillin and 37% to oxacillin. Klebsiella showed 100% sensitivity to ciprofloxacin and...