The goal of this project is to collect blood or skin tissues from subjects with liver disease to learn more about the factors that predispose individuals to their conditions. We are focusing our attention on subjects with two specific liver diseases: hepatitis C and non-alcoholic steatohepatitis (the latter is termed “NASH” or “fatty liver disease”). These are the two most common causes of liver disease in California. In the case of hepatitis C, research to date shows that factors such as race, genetic makeup and immunologic makeup influence individual responses to infection by the hepatitis C virus as well as responses to antiviral drug treatment. Our goal is to recruit individuals with diverse backgrounds and responses to hepatitis C infection and treatment, to enable scientists to identify the determinants of susceptibility or resistance to hepatitis C-related liver disease. In the case of fatty liver disease, we are recruiting subjects who have significant liver injury due to the accumulation of fat, proven on a liver biopsy (NASH). NASH is typically found in subjects who are overweight, and who often have additional health problems such as high blood pressure, high cholesterol and diabetes. We are also looking for subjects who are at risk for NASH and have prominent fat accumulation in the liver on a biopsy, but have no evidence of actual liver injury. As with hepatitis C, the goal with fatty liver disease is to accumulate a cohort of subjects with diverse backgrounds and a spectrum of disease severity, to enable scientists to determine the factors that predispose some individuals at risk to serious liver disease while sparing others.