The interactions between methylated $eta$-cyclodextrin (CD) and hydrophobically modified alkali-soluble associative polymers (HASE) were examined by a rheological technique. The effect of "capping" of hydrophobes by methylated $eta$-cyclodextrin on the viscosity and modulus was evaluated. Model HASE polymers with $C_1$to $C_{20}$ alkyl hydrophobic groups ethoxylated with~10 moles of ethylene-oxide (EO 10) and at concentrations up to 3 wt% were examined. With the addition of methylated $eta$-CD, the steady shear viscosity profiles shift from a Newtonian profile to one that display a shear-thinning characteristic. Significant "capping" of the hydrophobes occurs for HASE polymers with $C_{l2}$, $C_{16}$ and $C_{20}$ hydrophobes as reflected by the large reduction in the viscosity. However, the steady shear viscosity remains constant when the concentration of $eta$-CD exceeds 1 wt%, suggesting that $eta$-CD is not able to fully encapsulate the hydrophobes of the HASE polymer. The temperature variation plots indicate that the activation energy of the HASE-EO10-$C_{20}$ system and $eta$-CD is dependent on the magnitude of the applied shear stress. These results further reinforce the hypothesis that $eta$-CD is not able to completely remove all the hydrophobic associations.phobic associations.