Obesity-related steatosis is an increasingly common histological finding in liver biopsies and may co-exist with other chronic liver diseases. Although non-alcoholic fatty liver disease (NAFLD) without true steatohepatitis is generally a benign condition, when another liver disease is present, steatosis may exacerbate the liver damage. In this review, we discuss the interaction of obesity-related steatosis with chronic hepatitis C, alcoholic liver disease, disorders of hepatic iron storage and drug-induced liver disease. The role of weight reduction in minimizing liver injury in patients with chronic hepatitis C is discussed. Finally, we discuss the problems associated with orthotopic liver transplantation for patients with NAFLD.