The incidence of cirrhosis increase every year; major complications, late diagnosis and therapeutic difficulties contribute to a reserved prognosis. The present work addresses to the study of ascites and spontaneous bacterial peritonitis (SBP), some of the most common complications of hepatic cirrhosis, with important mortality. This book opens new perspectives of a possible elucidation of the pathogenesis of SBP and highlights the need for a therapy aimed to reduce oxidative stress and restore intestinal flora.