A series of 4,5-diaryl-2-(substituted thio)-1H-imidazoles was synthesized and evaluated as antiinflammatory and analgesic agents in the rat adjuvant induced arthritis assay and the mouse phenyl-p-benzoquinone writhing (PQW) assay. Several analogues were found to be more potent than phenylbutazone and indomethacin. Structure-activity relationships are discussed. One of the compounds, 4,5-bis(4-fluorophenyl)-2-[(1,1,2,2-tetrafluoroethyl)-sulfonyl]-1H- imidazole (8d, tiflamizole), was found to be 8 times as potent as indomethacin in the rat adjuvant induced arthritis assay and is presently undergoing clinical trial as an antiarthritic drug.