A series of aromatic poly(thioether ketone)s were synthesized from 4,4'-dimercaptodiphenyl ether (I) and 4,4'-dimercaptodiphenyl thioether (II), by reaction with a series of ketone-activated aromatic fluoro compounds (IIIa-e) in DMF in the presence of anhydrous K2CO3. Two poly(thioether phenyl phosphine oxide)s were also prepared from bis(4-fluorophenyl)phenyl phosphine oxide (IV). The aromatic polythioethers had inherent viscosities of 0.3-0.88 dL/g. All polymers were amorphous and soluble in such solvents as CHCl3, DMF, DMAc, NMP, and DMSO. The glass transition temperatures of these aromatic polythioethers were in the 154-251 degrees C range, and the 5% weight loss temperatures in TGA were in the 420-541 degrees C range in N-2 and the 503-527 degrees C range in air. Wide-angle x-ray diffraction data on selected polymers showed that the polymers were amorphous.