Urinary tract infections (UTIs) are common clinical problem in pediatric hospitals. The aim of this study was to compare the incidence of UTIs during two different time periods (from February 1999 to March 2000, and from April 2000 to September 2001) in pediatric patients treated in ambulatory or hospitalized in new children hospital. The frequency of occurrence of ESBL--producing Gram-negative rods increased during second period study. The isolated ESBL--producing strains were resistant also to aminoglicosides and trimethoprim/sulfamethoxazol Gram-negative rods were predominant microorganisms. Isolated organisms from urine samples included Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, Proteus mirabilis, Proteus penneri, Proteus vulgaris, Morganella morganii, Citrobacter freundi, Serratia spp., Enterobacter cloacae, Pseudomonas aeruginosa, Staphylococcus aureus, CNS, Enterococcus spp. Streptococcus spp, and Candida spp. Enterococcus spp. were isolated from urine samples in 20% of cases. Only 9.4% of isolated Enterococcus spp. were high-level aminoglicoside resistant (HLAR) strains. No vancomycin-resistant Enterococcus spp. were isolated. Among coagulase-negative Staphylococci (CNS) methicillin resistant strains (MRCNS) were isolated in 43.3%.