Concurrent hepatitis C virus (HCV), hepatitis delta virus (HDV), or human immunodeficiency virus (HIV) infection with chronic hepatitis B virus (HBV) appears to increase the risk of progressive liver disease including liver cirrhosis and hepatocellular carcinoma. There is a 10% prevalence of HCV infection in chronic HBV or HDV infection. Serological evidence of previous exposure to HBV is found in more than 80% of HIV-positive patients in the high risk group. Notably, the most recently acquired virus tends to suppress the pre-existing virus. In chronic HBV infection acquired perinatally or in early childhood, usually HCV is dominant and may suppress or even displace HBV and HDV. Less frequently, HBV or HDV suppresses HCV. It is generally agreed that the dominant virus should be identified in order to make appropriate treatment decisions. Studies with standard interferon (IFN) to treat patients with HCV dominantly dual HBV/HCV infection have showed only limited virological response. But high dose of IFN has been demonstrated with better response rate. Combined ribavirin with standard or pegylated IFN therapy could achieve a sustained HCV clearance rate comparable with those infected with HCV alone. On the contrary, patients with HBV dominantly dual viral infection might indicate more appropriate addition of lamivudine to IFN than ribavirin. Additionally, patients with concurrent infection of HBV and HDV, IFN seems to be the only effective agent. However, the efficacy of IFN is related to the dose. High dose of IFN [9 MU tiw (thrice per week)] and longer treatment duration (at least 2 years) have been shown to achieve adequate virological response. In patients with concurrently infected HBV and HIV, anti-HBV therapy should be considered for all patients with evidence of liver disease, irrespective of the CD4 cell count. In patients not requiring antiretroviral therapy, HBV therapy should be preferentially based on IFN, adefovir, or telbivudine. In contrast, in patients with CD4 cell counts <350 cells/mul or those already on antiretroviral therapy, agents with double anti-HBV and anti-HIV activity are preferred. At present, the evidence of therapeutic efficacy is not sufficient to make a recommendation in treating patients with dual HBV/HCV or HBV/HDV or HBV/HIV infection. Further studies of the well-designed, larger scale are needed to elucidate the role of different regimens or combination in the treatment of dual viral infection.