The structure of the previously reported new antiinflammatory agent (1, FK3311) was chemically modified in an attempt to find novel compounds with more potent and broader-spectrum activities. Some 2'-(phenylthio) and 2'-(phenylamino)methanesulfonanilides (2 and 3), in particular those bearing an electron-attracting substituent at the 4'-position, potently inhibited adjuvant arthritis in rats as well