Summary. Only HBV chronically infected patients with ongoing viral replication, high levels of ALT and histological aggres- siveness are considered candidates for interferon therapy. The superiority of pegylated interferon over recombinant interferon is remarkable especially in »hard to treat« patients (cirrhosis). Lamivudine therapy is safe and effective in terms of HBV suppres- sion, ALT normalization and improvemet in histology. The emergence of YMDD mutations of HBV during therapy is not only associated with viral and biochemical breakthroug, but hepatitis flared and even hepatic decompensation may also develop. Adefovir dipivoxil demonstrates significant clinical and antiviral benefits in chronic hepatitis B (HBeAg positive and negative), patients with lamivudine-resistant HBV, and pre-as well as post-liver transplantation patients with compensated and decom- pensated liver function. Current therapy with pegylated interferons and ribavirin is effective in around one-half of previously untreated patients with chronic hepatitis C. Early virological response three months after the beginning of therapy can be used to predict treatment outcome, and therapy can be stopped in those patients who did not become viral undetectable or whose viral level did not decrease by 2-log units or greater. Most patients with HCV infection will develop recurrence after liver transplantation. Combination therapy with interferon and ribavirin are encouraging but limited by the high rate of side effects in the early posttransplat period.