The current standard treatment for chronic hepatitis C consists of the combination of pegylated interferon and ribavirin. Although interferon is known to have potent antiviral, immunomodulatory, and anti-inflammatory activities against hepatitis C, the mechanism of ribavirin action against this virus is not clearly understood. This article will review proposed mechanisms of ribavirin activity, along with their supporting data, covering ribavirin's roles in the direct inhibition of hepatitis C viral replication, the inhibition of inosine monophosphate dehydrogenase, the induction of mutagenesis to the threshold of error catastrophe, and immunomodulation.