3Ietalation of 2-trifluoromethylphenothiazine followed by carbonation of the metallo intermediates leads to the foimation of a mixture of 2-trifluoromethyl-and 8- trifluoromethylphenothiazine-1-carboxylic acids, with the first, material predominating. Both compounds exhibit antiinflammatory properties in experimental animals, with the 8 isomer being the more potent.