Poly(arylene thioether)s (PTEs) containing 9,9'-spirobifluorene moieties were synthesized in high yields from 9,9'-spirobifluorene-2,2'-bis(N,N-dimethylcarbamothioate) 4 as the masked dithiol and various difluoroarenes as electrophilic monomers. All PTEs showed high thermal stability: The 10% weight loss temperature as evaluated by thermogravimetric analysis was over 470 degrees C under both nitrogen and air atmospheres. The glass transition temperature estimated by DSC was in the range 210-270 degrees C. The PTEs showed high solubility in ordinary organic solvents, such as CHCl3, NMP, and THF. Most PTEs exhibited remarkably high refractive indices ranging from 1.69 to 1.73 at 587.6 nm, whereas no or little birefringence was observed for the PTEs. (c) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4192-4199, 2010