In Egypt, schistosomiasis was traditionally the most important public health problem and infection with Schistosoma mansoni the major cause of liver disease. From the 1950s until the 1980s, the Egyptian Ministry of Health (MOH) undertook large control campaigns using intravenous tartar emetic, the standard treatment for schistosomiasis, as community-wide therapy. This commendable effort to control a major health problem unfortunately established a very large reservoir of hepatitis C virus (HCV) in the country. By the mid-1980s, the effective oral drug, praziquantel, replaced tartar emetic a s treatment f o r schistosomiasis in the entire country. This both reduced schistosomal transmission and disease and interrupted the "occult" HCV epidemic. It was evident when diagnostic serology became available in the 1990s that HCV had replaced schistosomiasis as the predominant cause of chronic liver disease. Epidemiological studies reported a high prevalence and incidence of HCV, particutarly within families in rural areas endemic for schistosomiasis. Clinical studies showed 70% to 90% of patients with chronic hepatitis, cirrhosis, or hepatocellular carcinoma had HCV infections. Co-infections with schistosomiasis caused more severe liver disease than infection with HCV alone. Schistosomiasis was reported to cause an imbalance in HCV-specific T-cell responses leading to increased viral load, a higher probability of HCV chronicity, and more rapid progression of complications in co-infected persons. As complications of HCV usually occur after 20 years of infection, the peak impact of the Egyptian outbreak has not yet occurred. Efforts have been initiated by the Egyptian MOH to prevent new infections and complications of HCV in the estimated 6 million infected persons.