Interferon alpha has confirmed its efficacy for the therapy of chronic hepatitis C. Half of the patients treated will normalize their plasma ALT at the end of a 6-month course of 3 MU thrice a week. This biochemical response is associated with a reduction of HCV RNA (viraemia) from serum and with significant improvement of liver histology. Despite those beneficial effects, 50% of treatment responders generally relapse after treatment arrest. Increasing doses to 6 MU and/or the duration of interferon therapy increases the proportion of long-term sustained responders. Combining therapy with ribavirin, a nucleoside analogue, also appears to have a similar effect.