The term Non-Alcoholic Steatohepatitis (NASH) was introduced to describe a group of patients in whom liver biopsy shows the typical morphology of Alcoholic Steatohepatitis, without the presence of any significant alcohol consumption. The presence of steatosis and inflammatory infiltrate in liver biopsy is essential for the diagnosis of NASH. Other chronic liver diseases--such as Hepatitis B and C as well as Autoimmunohepatitis--which can cause similar morphologies have to be excluded. The pathophysiology of NASH is essentially still unclear. On the one hand toxic effects of oxidated fatty acids are suspected, on the other hand it is postulated that the fatty liver is very vulnerable and that actual hepatitis is triggered by an additional stressor. The disease has a benign clinical course and the typical patient is asymptomatic with elevated liver enzymes. Despite the paucity of symptoms the risk of cirrhosis is approximately 8-17%. No established treatment exists. Preliminary reports suggest a positive effect of gradual weight loss and ursodeoxycholic-acid but further studies are needed to confirm this observation.