Regulatory T cells are a subtype of T-cells that play a fundamental role in maintaining immune homeostasis to balance between the tissue-damaging and protective effects of the immune response. Regulatory T cells are characterized by the expression of the Forkhead box protein P3 transcription factor in the nucleus and is generally accepted as the single best marker for regulatory Tcells. In cases of hepatitis c virus infection, the role of regulatory Tcells is still controversial and most of studies yielded conflicting reports. This conflict may be explained by the heterogeneity in the methods and sites of studying the frequency of regulatory T cells.