In this study, poly(2-acrylamido-2-methyl-1-propane sulfonic acid) (PAMPS) was synthesized using potassium persulfate (K2S2O8) as initiator. PAMPS ((M) over bar (n) = 36,000 g/mol) was partially converted to a lithium salt (PAMPS-Li), and particle size was determined to be 40 gm. Suspensions of PAMPS-Li at various concentrations were prepared in silicone oil, mineral oil, dioctylphthalate (DOP), and trioctyltrimellitate (TOTM) insulating oils. Colloidal stabilities of these suspensions were determined at 20 and 80degreesC. The PAMPS-Li suspensions were observed to provide an electrorheological (ER) response upon the application of an external dc electric field. ER properties of these suspensions were investigated at various shear rates () and electric field strengths (E). Further, effects of polar promoters and high temperature on ER activity were determined, and excess shear stresses (AT) were calculated. A shear-thinning nonNewtonian viscoelastic behavior was observed for the PAMPS-Li suspensions.