Infection with hepatitis A virus (HAV) can cause severe illness in adult patients with chronic liver disease (CLD) caused by hepatitis C. In endemic areas such as South Asia, however, most adult patients already have been exposed to HAV but could still be susceptible to hepatitis E virus (HEV) infection. We document that HEV superinfection in 4 of our CLD patients caused severe liver decompensation. We then determined the seroprevalence of HAV and HEV in 233 patients with stable CLD, with the goal of defining the need for protection against these viruses in these patients. Overall, 41 (17.5%) of 233 CLD patients were HEV antibody immunoglobulin G (IgG)-positive, and 228 of 233 (97.8%) were HAV IgG-positive. As controls, we tested 90 age- and sex-matched healthy volunteer blood donors for HAV and HEV antibodies IgG. There was no difference in the percentage of CLD patients and blood donors positive for HEV antibody IgG (17.7% vs. 17.5%) or for HAV IgG (97.8% vs. 94%). No differences were observed in the severity of liver disease between previously HEV-exposed and-nonexposed patients. In conclusion, superinfection with HEV in patients with underlying CLD can cause severe hepatic decompensation leading to increased morbidity and mortality. The large majority of adult CLD patients in endemic countries are vulnerable to infection with HEV, but are protected against hepatitis A, and are ideal candidates for an HEV vaccine.