In conclusion, our study is the first to indicate that the peg-IFN α-2a 90 μg/week dose is as effective as peg-IFN α-2a 180 μg/week when combined with ribavirin in the treatment of chronic hepatitis C, but suggesting a better tolerability of the peg-IFN α-2a 90 μg/week plus ribavirin. This evidence concerns the gene IFNA1 and chronic hepatitis C virus infection.