A device is disclosed for determining the dynamic mechanical properties, cifically, G*, G', G", and Tan .delta., of an electrorheological (ER) fluid as a function of frequency, voltage and temperature. This is accomplished by using the device in conjunction with a suitable driving and environmental control apparatus. An inner tubular electrode, coaxial with an outer tubular electrode, is oscillated along their common longitudinal axis at frequencies in a range of approximately 5 Hz to approximately 1,000 Hz while the spacing between the electrodes is maintained substantially constant at all opposed portions thereof. A power source provides an electrical field encompassing the inner and outer electrodes and the gap therebetween, and the assoicated driving and environmental control apparatus is operated for measuring the effort required to move the second electrode relative to said first electrode when the ER fluid is received between said inner and outer electrodes. Such measured effort is a function, respectively, of the characteristics of the ER fluid, the rate of oscillation of said second electrode, the strength of the electrical field, and the temperature of the ER fluid.