Introduction Urinary tract infections (UTI) are among the most common infectious diseases affecting all age groups, from infants to the elderly. The majority of these infections occur in otherwise healthy individuals who present with symptoms of acute uncomplicated bacterial cystitis or pyelonephritis. Certain patient populations with complicated conditions are at increased risk for acquiring infection or failing therapy. Forty to 50% of adult women have a history of at least one urinary tract infection. Diagnosis and classification of UTI Although there are general guidelines concerning diagnosis and classification of urinary tract infections, there are wide variations in clinical practice. There are both errors which are frequently committed and mysteries that are still unsolved. Active management is important because under some circumstances urinary tract infections may cause permanent renal scarring. Imaging procedures are a cornerstone for critical evaluation of urinary tract infections, but avoidance of investigative routines will allow a marked saving in terms of costs and in terms of unnecessary radiation and psychological stress to the patient.