Urinary tract infections are a common problem for women and frequently result in a visit to the Emergency Department. Most of these infections are easily diagnosed and treated; however, subclinical pyelonephritis is a recently recognized entity and signs of upper tract involvement should always be sought, especially in compromised hosts and patients who are at risk for developing complicated infections. Each of these situations demands a more thorough evaluation and more prolonged and aggressive treatment to minimize the possibility of renal damage. Fortunately, there is a narrow spectrum of organisms responsible for most urinary tract infections, and they respond well to a wide range of commonly used antibiotics. Newer diagnostic techniques, the acceptance of short-course therapy for lower tract infections, and the development of new antibiotics have increased our diagnostic and therapeutic options. Further developments in these areas, as well as the possibility of nonantibiotic prevention of urinary tract infections, predict a brighter future for patients with complicated or frequently recurring urinary tract infections.