Vitamin D is an important secosteroid hormone with known effect on calcium homeostasis,but recently there is increasing recognition that vitamin D also is involved in cell proliferation and differentiation,has immunomodulatory and anti-inflammatory properties.Vitamin D deficiency has been frequently reported in many causes of chronic liver disease and has been associated with the development and evolution of non-alcoholic fatty liver disease(NAFLD)and chronic hepatitis C(CHC)virus infection.The role of vitamin D in the pathogenesis of NAFLD and CHC is not completely known,but it seems that the involvement of vitamin D in the activation and regulation of both innate and adaptive immune systems and its antiproliferative effect may explain its importance in these liver diseases.Published studies provide evidence for routine screening for hypovitaminosis D in patients with liver disease.Further prospectives studies demonstrating the impact of vitamin D replacement in NAFLD and CHC are required. Vitamin D is an important secosteroid hormone with known effect on calcium homeostasis, but recently there is increasing recognition that that vitamin D also is involved in cell proliferation and differentiation, has immunomodulatory and anti-inflammatory properties. Vitamin D deficiency has been frequently reported in many causes of chronic liver disease and has been associated with the development and evolution of non-alcoholic fatty liver disease (NAFLD) and chronic hepatitis C (CHC) virus infection. The role of vitamin D in the pathogenesis of NAFLD and CHC is not completely known, but it seems that the involvement of vitamin D in the activation and regulation of both innate and adaptive immune systems and its antiproliferative effect may explain its importance in these liver diseases.Published studies provide evidence for routine screening for hypovitaminosis D in patients with liver disease. Further prospectives studies demonstrating the impact of vitamin D replacement in NAFLD and CHC are requ ired.