The efficacy of Shosaiko-to (SST) on 222 patients with chronic active hepatitis was studied in a double-blind multicenter clinical study. One hundred and sixteen patients received SST in a daily oral dose of 5.4 g for 12 weeks, followed by the same dose for a further 12 weeks. One hundred and six patients received a placebo containing 0.5 g of SST for 12 weeks, followed by a cross-over to SST for a further 12 weeks. Among the liver tests, serum AST and ALT values decreased significantly with the administration of SST. The difference of the mean value between the SST group and the placebo group was significant after 12 weeks. In patients with chronic active type B hepatitis, a tendency towards a decrease of HBeAg and an increase of Anti-HBe antibodies was also observed. No remarkable side effects were noticed.