Hepatitis C virus (HCV) is considered the most common etiology of chronic liver disease (CLD) in Egypt, where prevalence of antibodies to HCV (anti-HCV) is approximately 10-fold greater than in the United States and Europe. Reported are results that show the role of HCV in both overt and occult CLD, the risk factors for CLD and for HCV infection, and the relative importance of chronic HCV, hepatitis B, or both in causing hepatic morbidity. Case patients included 237 new outpatients at the National Liver Institute. Controls comprised 212 sex- and age-matched neighbors without liver disease. Case patients were more likely than controls to report a history of blood transfusions, schistosomiasis, or parenteral therapy for schistosomiasis; to have anti-HCV, HCV RNA, hepatitis B surface antigen, and serum alanine aminotransferase (ALT) elevations; and to have abdominal ultrasound findings of cirrhosis, portal hypertension, and splenomegaly. Anti-HCV-positive case patients were more likely than anti-HCV-negative patients to be male, older, and farmers: to have received a blood transfusion or parenteral therapy for schistosomiasis; to have ALT elevations; and to have ultrasound findings of cirrhosis, portal hypertension, and spleen enlargement. Anti-HCV-positive controls were more likely than anti-HCV-negative controls to have received parenteral therapy for schistosomiasis. These data support the belief that HCV is the predominant cause of CLD in Egypt and suggest there is a large underlying reservoir of HCV-caused liver disease.