In this paper, we present a newly developed rare earth modified amorphous barium strontium titanate (BaxSr1-xTiO3) gel/silicone oil electrorheological (ER) fluid. The ER behaviors of suspensions of pure and rare earth modified amorphous BaxSr1-xTiO3 particles in silicone oil have been investigated under a dc electric field. The shear yield stress of the rare earth modified amorphous BaTiO3 gel/silicone oil ER fluid could reach 14.9 kPa at E = 3.5 kV/mm while the leaking current density was very low. about 7.64 muA/cm(2). The FR fluids with a higher volume fraction had a higher current density and a higher shear yield stress under the same electric field. The ER fluid has a long-term stability against sedimentation. The problem of caking was not serious and the agglomerated particles could be easily broken, up by strongly stirring, (C) 2004 Elsevier Inc. All rights reserved.