Nonalcoholic steatohepatitis (NASH) is a reasonably well-defined clinicopathological entity; it has been reported more commonly in women than in men or children of both sexes and it appears to be most closely associated with obesity, diabetes mellitus and related abnormalities, such as hyperlipidaemia and hyperglycaemia. However, the association with female gender, obesity and diabetes may not be as close as suggested by the literature and an underlying condition cannot be discerned in all cases. The natural history of the disease is poorly understood; the associated biopsy features span a wide spectrum, reaching from uncomplicated, clinically non-progressive fatty liver (not NASH in a strict sense) to a slowly progressive fatty liver with inflammation and fibrosis, to steatohepatitis with submassive hepatic necrosis, which has a subfulminant course and is often fatal. Non-progressive fatty liver appears to be very common but is of little clinical importance. The slowly progressive form of the disease represents NASH as encountered by most clinicians and pathologists. It is a common liver disease in current practice; patients may present with cirrhosis and even HCC arising from steatohepatitic cirrhosis. Subfulminant NASH has become exceedingly rare because many clinicians are now aware of the hazards of sudden weight loss, particularly in morbidly obese patients. Treatment options for NASH are still limited. The promotion of gradual weight loss in obese patients is the most widely recommended therapy but, unfortunately, this is very difficult to achieve. Avoidance of precipitous weight loss and careful control of diabetes mellitus are important and undisputed parts of patient management. Administration of UDCA as a treatment of NASH is still under study; it may be effective in some patients. The treatment of established steatohepatitic cirrhosis does not differ substantially from that of other types of cirrhosis and includes orthotopic liver transplantation.