To assess whether therapy with Ribavirin may affect the course of chronic delta hepatitis, nine Italian patients with this disease received the drug orally at a dosage of 15 mg/kg daily for 16 weeks. At the end of the therapy period, all patients were followed for 12 additional months. Seven patients completed the trial. Two patients were withdrawn: one developed hemolytic anemia, and the other intractable itching. At the end of treatment HD viremia was reduced in one patient, had cleared in another, and was unchanged in the remaining five patients. None of the patients decreased their alanine transferase (ALT) levels by more than 50%. At the doses given in this study. Ribarivin did not show significant antiviral effects in chronic hepatitis D, and was not effective in reducing the biochemical markers of liver inflammation and necrosis.