Study design. A randomised, controlled, open-label, 2-armed, parallel-group study comparing the safety and efficacy of oral antibiotic (10 days of amoxicillin + clavulanic acid 50 mg/Kg/day), vs initial iv treatment (ceftriaxon 50 mg/Kg/day until defervescence) followed by oral treatment (amoxicillin + clavulanic acid) for a total of 10 days, in children with a first episode of UTI.