One-hundred women suffering from acute pyelonephritis were hospitalized for less than 4 days on average, in order to make a diagnosis based on bacteriology and computerized tomography (CT) and to bring fever down with a 21-day antibiotic therapy. In cases of acute pyelonephritis due to a urinary tract obstacle, endoscopic uereteral drainage was added to the antibiotic treatment. In the absence of obstacle, medical treatment was sufficient to obtain apyrexia. Fluoroquinolone therapy made it possible to reduce the hospital stay to 2 or 3 days, depending on whether the lesions observed at CT were triangular or round.