Ribavirin (RBV) shows a strong antiviral effect on hepatitis C virus when used in combination with interferon. However, RBV-induced anaemia is a major problem in this therapy. It would be of great clinical importance to ameliorate the anaemia without reducing the RBV dose. Japanese researchers report that Ninjinyoeito (NYT), a herbal medicine, can reduce the RBV-induced anaemia. Twenty-three patients with chronic hepatitis C were treated with interferon alpha 2b plus RBV with (NYT group) or without (control group) NYT by randomised selection. Eighteen patients completed the treatment schedule, and haemato-biochemical and virological effects were evaluated. There was no significant difference in biochemical and virological responses between the two groups. However, anaemia was significantly reduced in the NYT group compared with the control group. The maximal decrease of haemoglobin in the NYT group (2.59±1.10 g/dl) was significantly smaller than that in the control group (3.71±0.97 g/dl). There was no significant difference in serum glutathione per-oxidase activity, serum RBV concentration or T-helper1/T-helper2 balance between the two groups. There was no specific adverse effect in NYT administration.