Hepatitis C virus(HCV) infection and diabetes mellitus are two major public health problems that cause devastating health and financial burdens worldwide. Diabetes can be classified into two major types: type 1 diabetes mellitus(T1DM) and T2 DM. T2 DM is a common endocrine disorder that encompasses multifactorial mechanisms, and T1 DM is an immunologically mediated disease. Many epidemiological studies have shown an association between T2 DM and chronic hepatitis C(CHC) infection. The processes through which CHC is associated with T2 DM seem to involve direct viral effects, insulin resistance, proinflammatory cytokines, chemokines, and other immunemediated mechanisms. Few data have been reported on the association of CHC and T1 DM and reports on the potential association between T1 DM and acute HCV infection are even rarer. A small number of studies indicate that interferon-α therapy can stimulate pancreatic autoim-munity and in certain cases lead to the development of T1 DM. Diabetes and CHC have important interactions. Diabetic CHC patients have an increased risk of developing cirrhosis and hepatocellular carcinoma compared with nondiabetic CHC subjects. However, clinical trials on HCV-positive patients have reported improvements in glucose metabolism after antiviral treatment. Further studies are needed to improve prevention policies and to foster adequate and cost-effec-tive programmes for the surveillance and treatment of diabetic CHC patients. Diabetes can be classified into two major types: type 1 diabetes mellitus (T1DM) and T2 DM. T2 DM is a common endocrine disorder that encompasses multifactorial mechanisms, and T1 DM is an immunologically mediated disease. Many epidemiological studies have shown an association between T2 DM and chronic hepatitis C (CHC) infection. The processes through which CHC is associated with T2 DM seem to involve direct viral effects, insulin resistance, proinflammatory cytokines, chemokines, and other immunemediated mechanisms. Few data have been reported on the association of CHC and T1 DM and reports on the potential association between T1 DM and acute HCV infection are even rarer. A small number of studies indicate that interferon-α therapy can stimulate pancreatic autoimmunity and in certain cases lead to the development of T1 DM. Diabetes And CHC have important interactions. Diabetic CHC patients have an increased risk of developing cirrhosis and hepatocellular carcinoma compared with nondiabetic CHC subjects. However, clinical trials on HCV-positive patients have reported improvements in glucose metabolism after antiviral treatment. Further studies are needed to improve prevention policies and to foster adequate and cost-effec-tive programs for the surveillance and treatment of diabetic CHC patients.