The most significant finding in this study was the association between KIR-HLA receptor-ligand pairings and treatment outcome in chronic hepatitis C. Among the inhibitory KIR-HLA receptor-ligand pairs, patients with KIR3DL1-HLA-Bw4 exhibited a significantly higher SVR rate when compared to those without this pair (P = 0.03; OR 2.29). This evidence concerns the gene KIR3DL1 and chronic hepatitis C virus infection.