Complications resulting from persistent and repeated urinary tract infections (UTIs) account for nearly 1 million hospital admissions annually. Cystitis, a localized bladder infection occurring in the lower tract, is recognized by a symptom complex of dysuria, frequency, urgency, and suprapubic tenderness; pyelonephritis, which refers to upper tract infection of the kidneys, classically manifests with flank pain and systemic as well as cystitis signs. An empiric 3-day antibiotic regimen has been shown to be more than 95% effective in curing cystitis. But for a subgroup of patients, a relapse of "cystitis" within 4 weeks can signal a subclinical, "silent," pyelonephritis. A 14-day course of antibiotics is indicated to treat the recurrent UTI. Follow-up urinalysis and urine cultures are then repeated 2 and 4 weeks after therapy. If symptoms and/or bacteriuria are again documented with the same organism, subclinical pyelonephritis is presumed; a prolonged 6-week course of antibiotics is then warranted to prevent prolonged problems and complications associated with UTIs. When the problem is reinfection with a microorganism different from that responsible for the last infection, short-course therapy for 3 days may be prescribed for each episode. When reinfection occurs more frequently than 2 to 3 times a year, however, antibiotic prophylaxis to prevent reinfections is warranted.