A series of 2-(4-methylphenyl)benzothiazoles was synthesized and evaluated using an adjuvant-induced arthritic rat model. This calss of desired compounds affecting the immune response was found using hemagglutination assay.4-Acetoxy-2-(4-methylphenyl)benzothiazole (7m), KB-2683, was most potent in the adjuvant-induced arthritic rat model and selected for further evalution. In contrast to nonsteroidal antiinflammatory drugs, compound 7m showed no antiinflammatory or analgesic activities. It did, however, show an immunomodulatory activity in enhanced delayed type hypersensitivity.