Our data suggest no significant difference between interferon a-2a or 2b, which suggest it is not due to the interferon molecule. In most interferon monotherapy cases of interstitial pneumonitis in HCV treatment in Japan the use of Sho-Saiko-to, a herbal medicine, led to pneumonitis. Sho-Saiko-to has been approved by the Japanese Ministry of Health and Welfare and has often been administered in chronic viral liver disease [27] .