Competition between the aggregation of the octadecyl substituents of 3% randomly substituted poly(acrylate), PAAC18, and of the dodecyl substituents of the PAAC12 analogue, and their complexation by beta-cyclodextrin, beta CD, the linked dimers, N,N'-bis(6(A)-deoxy-6(A)-beta-cyclodextrin)urea, 66 beta CD(2)ur, and N,N'-bis(6(A)-deoxy-6(A)-beta-cyclodextrin)succinamide, 66 beta CD(2)su, and gamma-cyclodextrin, gamma CD, and the analogous dimers 66 gamma CD(2)ur and 66 gamma CD(2)su have been studied in aqueous solution. The zero-shear viscosities of 3.3 wt % aqueous solutions of PAAC18, decreases in the presence of beta CD, 66 beta CD(2)ur, 66 beta CD(2)su and gamma CD, is little changed in the presence of 66 gamma CD(2)ur, and increases in the presence of 66 gamma CD(2)su. In contrast, the zero-shear viscosities of aqueous solutions of PAAC12 increase in the presence of beta CD, gamma CD, and their dimers but they are much less than those of the corresponding PAAC18 solutions. These macroscopic variations are due to host guest complexation of the octadecyl and dodecyl substituents by beta CD, gamma CD, and their dimers (as shown by 2D H-1 NOESY NMR spectroscopy) competing with aggregation of the octadecyl and dodecyl substituents where differences in substituent length and cyclodextrin annular size are dominant factors.