The term complicated urinary infections (CUIs) includes infections developing in the presence of anatomic anomalies, metabolic or hormonal disorders, immunodeficiency or infection with atypical microorganisms. Complicating factors diminish efficiency of antibiotic treatment, raise probability of recurrence. CUIs account for 45.2% of all cases of outpatient urinary infections in adults in Russia. Nephroliths, diabetes mellitus and renal cysts are most prevalent complicating factors. CUIs causative agents' spectrum is wider and resistance bacteria isolation is more frequent compared to uncomplicated urinary infections. In addition to antibiotic therapy, CUIs treatment should be focused on detection and elimination of the complicating factor. If complicating factors are unremovable, antibiotic therapy should be directed to management of clinical symptoms of urinary infection, prevention of complications and damage to renal parenchyma. CUIs demand longer courses of antibiotics than uncomplicated urinary infections: 7-14 days in infection of the lower urinary tracts, at least 14 days in infection of the upper urinary tracts and 4-6 weeks in failure of the standard course. Fluoroquinolones are drugs of choice in adults.