Two polymers containing different amphiprotic groups were synthesized and were characterized with FT-IR spectroscopy, thermogravimetric analysis and scanning electron microscopy. Several anhydrous electrorheological (ER) fluids were prepared using two polymers as disperse phase and bromodiphenylmethane or silicone oil as disperse medium. Rheological measurements were performed via a Couette-type rheometer with a high voltage generator to investigate the effects of electric field strengths, disperse particle content and different disperse mediums on the ER behavior. Results showed that ER effects of the suspensions were enhanced by increasing polymer particle content and electric field strength. The polarized intensity of amphiprotic groups in the polymer is crucial to enhance ER effects of the suspensions. (C) 2010 Elsevier B.V. All rights reserved.