Hepatitis C virus (HCV) is the most common cause of chronic liver disease, cirrhosis, and hepatocellular carcinoma (HCC) in the United States and infects an estimated 170 million people worldwide. In the United States, overall hepatitis C prevalence is 1.8% and is higher in African Americans and Hispanics than it is in white Americans. The age distribution places 65% of all subjects with anti-HCV antibodies between 30 and 49 years of age. Before serological screening of blood products was initiated, hepatitis C was most commonly transmitted by transfusion of contaminated blood products, but now it is acquired primarily via intravenous drug use. Only 10 to 25% of infected adult patients spontaneously resolve their infection, and the remaining 75% remain persistently viremic and often asymptomatic. Progression of liver disease in 20 to 30% of patients can lead to compensated and eventually decompensated cirrhosis or hepatocellular carcinoma, or both. This article looks briefly at the epidemiology and natural history of hepatitis C.