In this study, the electrorheological ( ER) behavior of suspensions prepared from d(50) = 2.4 mu m talc powder, dispersed in insulating silicone oil ( SO) medium was investigated. Sedimentation stabilities of suspensions ( c = 5 wt%) prepared using these talc powder powders were determined to be 78 days. The ER activity of all the suspensions was observed to increase with increasing electric field strength, concentration and decreasing shear rate. The shear stress of talc powder suspensions increased linearly with increasing concentrations of the particles and with the applied electric field strength. Electric field viscosity of all the suspensions decreased sharply with increasing shear rate and showed a typical shear thinning non-Newtonian visco-elastic behavior. Effects of frequency on the ER activity of talc powder/SO system were also investigated.