A rotational rheometer with cone and plate fixtures was used to measure the intrinsic viscosities of aqueous suspensions of xanthan gum and carboxymethyl cellulose (CMC). The reduced viscosities or hydrodynamic volumes of CMC suspensions increased with dilution. However, the reduced viscosities of xanthan gum suspensions decreased with dilution within the concentration range of 0.1–0.06% and increased with dilution within the concentration range of 0.04–0.01%. When the gums were suspended and diluted with 0.06 M sodium acetate, the reduced viscosities of all the xanthan gum and CMC suspensions decreased upon dilution. The intrinsic viscosities of xanthan gum and CMC suspensions decreased with increasing the shear rate, showing a dependence of hydrodynamic volume on shear rate.