Urinary tract infections (UTIs) are an important cause of morbidity in paediatrics, especially related to urinary tract malformation and neurogenic bladder dysfunction. The infection control team of Istituto Giannina Gaslini, Genova, Italy, performs a prospective survey on the epidemiology of UTI in children admitted in the hospital, and data are expressed as episodes/1000 days of hospital admission. From 2007 to 2011 there was an increase in the rate of Gram-negative UTIs, especially in the Nephrology Unit (from 11.63 to 27.48, r-coefficient 0.95, P minor 0.05), associated with an increase in infections due to ESBL-producing strains (from 0.54 to 2.55, r-coefficient 0.89, P 0.05). This study indicates that there is an increase in the rate of Gram-negative UTIs, also due to resistant strains. The cause may be multifactorial, but it is noteworthy that it has been mainly observed in a ward where low-dose, long-term administration of antibacterial prophylaxis in children with urinary malformations or neurogenic bladder dysfunction is routine. This phenomenon gives cause for concern and should be monitored carefully to avoid the risk of selecting resistant bacteria that have no therapeutic options.