Abstract: The present invention relates to an electrorheological fluid composition comprising a dispersion of a plurality of solid particles in an electrically non-conducting liquid, the improvement comprising using as said solid particles a composition having the general formula:[(M).sup.p (H.sub.2 O).sub.x (OH).sub.y ].sup.q.sub.c [A].sup.r.sub.d.B.sub.z.nH.sub.2 Owherein M is a metal cation or a mixture of metal cations at various ratios; p is the total valence of M and has a value of greater than zero; x is zero or has a value greater than zero, y is zero or has a value greater than zero, with the proviso that only one of x or y can be zero at any given time; q has a value of p minus y with the proviso that q has a value of at least one; c has a value of greater than zero; A is an anion or a mixture of anions at various ratios; r is the total valence of A with the proviso that r has a value of at least one; d has a value of greater than zero with the proviso that (q.times.c) is always equal to (r.times.