Summary. Delta virus related chronic hepatitis is difficult to treat. The response to α-interferon (IFN), which still represents the only therapy for chronic hepatitis D, varies widely and occurs at different times from the beginning of treatment. The rate of response is proportional to the dose of IFN, with 9 million units (MU) three times a week being more effective than 3 MU thrice weekly. Sustained responses are unusual and are accompanied by the clearance of serum hepatitis B virus surface antigen (HBsAg), seroconversion to anti-HBs and improvement of liver histology. Although disease of a short-standing may respond better to therapy, clear predictors of response are still unidentified. Besides IFN, other therapeutic approaches such as immunosuppressive drugs, acyclovir, ribavirin and thymosin, have been unhelpful. Available evidence does not support the use of deoxynucleotide analogues. Famciclovir has no effect on disease activity and hepatitis D virus (HDV)-RNA levels. Twelve- or 24-month lamivudine treatment does not significantly affect biochemical, virological or histological parameters. Pegylated-IFN could represent a reasonable therapeutic option in the long-term treatment required for chronic hepatitis D. Antisense oligonucleotides and prenylation inhibitors hold promise as therapeutic agents of the future. Liver transplantation provides a valid option for end-stage HDV liver disease; the risk of re-infection is lower for HDV than for HBV under long-term administration of hyperimmune serum against HBsAg. Molecularly tailored drugs capable of interfering with crucial viral replicative processes of HDV appear to be the best prospect in the treatment of hepatitis D.