Steatosis has emerged as a histologic finding of importance to the progression of hepatitis C virus (HCV)-associated liver disease. However, most studies of HCV-associated steatosis have excluded alcohol drinkers and individuals with diabetes and thus have not addressed the relative contribution of known causes of steatosis to liver injury in HCV-associated disease. To address this issue, we studied 297 consecutive patients with HCV who met inclusion criteria. Alcohol consumption, demographics, and serologic tests were correlated with degrees of steatosis and fibrosis on liver biopsy. Liver biopsy specimens were also examined for evidence of significant alcohol or nonalcoholic steatohepatitis (NASH) injury. In univariate analysis, steatosis correlated with type 2 diabetes mellitus (P =.005) and body mass index (BMI) (P =.0001) but not with the intensity of alcohol intake (in grams per day). In multivariate analysis, BMI (P =.0002) and genotype 3a infection (P =.02) were independent predictors of steatosis. When patients with risk factors for NASH were excluded, genotype 3a infection was the only independent predictor of steatosis. Steatosis (P =.04) and inflammation (P <.0001) scores on liver biopsy were the only independent predictors of fibrosis. Significant alcohol or NASH injury was found in only 6% of biopsy specimens. In conclusion, steatosis in HCV infection is associated with risk factors for NASH, particularly obesity, rather than alcohol consumption.