Summary: Urinary tract infection (UTI) is a collective medical term that embraces a broad spectrum of clinical conditions ranging from simple cystitis in non-pregnant healthy women, easily treated in an outpatient setting, to severe, life-threatening urosepsis in immunocompromised patients. The article reviews the definitions, pathogenesis, microbiology, risk factors, clinical presentation, treatment, and prevention of different forms of UTI in the general population and selected groups such as pregnant women, patients with indwelling catheters, and patients after kidney transplantation.