Antimicrobial therapy for pyelonephritis in children must quickly eradicate the bacterial infection and prevent scars in renal parenchyma. Escherichia coli (E Coli) is found in about 90% of cases of acute pyelonephritis in outpatients, 40% of E coli being ampicillin-resistant. The present effective antibiotics are: 3rd-generation cephalosporines, amoxicillin-clavulanic acid association, and aminoglycosides. In the literature therapeutical guides are divergent concerning the route of administration (oral or i.v.), mono or bitherapy, the duration of the treatment (usually for 10 days), and the need for hospitalisation. The criteria for choice are risk factors such as: very young age (< 6 months), fever with toxic symptoms, vomiting, dehydration, uropathy, and poor compliance. There are few long term studies which compare two, therapeutic regimens and no evaluation of the frequency of consequent chronic pyelonephritis in adult age has taken place. Recent data suggest that an oral sequential treatment may permit a shorter hospital stage. The trend is chiefly to do bona fide recommendations more than elaboration of a true consensus.