To investigate steady shear rheology, a plate-plate type rota- tional rheometer was employed in this study. A schematic diagram of the rotational rheometer is shown in the Fig. 2. An electro- magnetic coil was placed under the sample holding plate and DC power supply was linked to allow current in the coil, generating magnetic field penetrating vertically and uniformly through the MR fluid samples. To measure the generated magnetic flux density, a thin transverse type probe is placed between the thin lower shear plate and the electromagnetic coil set. Both of upper shearing plate and lower fixed plate are made of non-magnetic material to exclude the effects from the interaction between the plates and generated magnetic field. A hot plate was also em- bedded in the rheometer to change the temperature of fluids. With this rheometer system, the shear viscosity of seven different samples was measured at three different temperatures of 40 oC, 70 °C and 110 oC under eleven different magnetic flux density of 0 100 mT, and shear rate in the regime of 5-500 1ls. While obtaining data, at high shear rates, wall slip is present, thus proper correc tion has to be made to account the effects of wall slip. Rabinowitch