The effects of Sokei-kakketsu-to, Yokuinin-to, Keisi-ka-zyutsubu-to, Eppi-ka-jutsu-to, and Saireito extracts on Adjuvant-induced arthritis (AA) in rats were investigated. After administering AA, we measured the volume of rat hindpaw as the inflammation index, and observed the changes of synovitis histologically. Each extract showed different effects on AA rats. Yokuinin-to and Sokei-kakketsu-to had remarkable effects on inflammation and changed the histological observations of synovitis. Eppi-ka-jutsu-to also had effects on the uninjected hindpaw, but Keisi-ka-jutsubu-to and Sairei-to had no effect on hindpaw inflammation, nor did they change synovitis histologically.