An electroviscous fluid comprising more than 25% by weight of silica gel with a water content of 1 to 15% by weight, a non-conductive oily phase dispersion medium, 1 to 30% by weight of one or more polymers soluble in the dispersion medium, the weight percentage being based on the water-containing silica gel, and the polymers having a molecular weight in the range of from 5.times.10.sup.3 to 10.sup.6 and containing 0.1 to 10% by weight of N and/or OH and 25 to 83% by weight of C.sub.4 to C.sub.24 -alkyl groups. Such electroviscous fluids are useful for transmitting powerful forces by means of a low electronic output, for example, in hydraulic valves and shock absorbers.