Host genetic variation may affect the outcome of chronic viral hepatitides, favoring viral clearance and/or modulating the inflammatory response to persistent infection. Our aims were to assess whether interleukin 6 (IL-6) promoter polymorphisms are associated with chronic hepatitis C virus (HCV) infection and to clarify the role of IL-6 haplotypes in facilitating progressive disease. The study included 424 Italian patients (233 males, median age 53 years) affected by HCV chronic infection. IL6 -1363, -597, -572, -174, and +2954 polymorphic loci were assayed by means of restriction fragment length polymorphism. Three hundred forty-four healthy Italian blood donors (245 males, median age 50 years) served as controls. Comparing patients and controls analysis of molecular variance was highly significant (p < 0.0001); at a locus by locus approach, the frequencies of minor alleles in the -1363 (p < 0.02), -597 (p < 0.02), and -174 (p < 0.01) polymorphisms were confirmed to be less represented in patients than in controls. Carrying the wild-type G allele at the -597 and -174 loci identified an unfavorable haplotype; carrying the minor allele in one/both loci identified an indifferent/favorable haplotype. Male patients carrying two unfavorable haplotypes had the highest adjusted mean ± standard error Ishak staging score (3.56 ± 0.19), while females carrying one or no unfavorable haplotypes had the lowest (2.69 ± 0.21); the remaining patients had an intermediate value (3.12 ± 0.13, p < 0.01). In conclusion, IL-6 promoter polymorphisms influence the development of chronic HCV infection. With the permissive effect of male gender, haplotypes represented by the wild-type allele for -597 and -174 loci appear to favor a worse evolution of the disease.