Among inflammatory disorders of the urinary tract, cystitis is the most common. A significant increase in the prevalence of this condition is reported by epidemiological investigations, and its diagnostic and therapeutic approach often represents a challenge. Bacterial cystitis is becoming difficult to treat, especially if chronic or recurrent, due to the increase of drug resistance among the responsible pathogens. Chronic non-infectious cystitis is also difficult to treat because its pathophysiologic mechanisms are still not completely understood. This book provides a comprehensive overview of bladder inflammation, focusing on etiopathogenesis, pathophysiology, and diagnostic and therapeutic approaches to the main types of infectious and non-infectious cystitis in both adults and children. It also addresses radiation cystitis as well as iatrogenic cystitis.