A host polymer with pending beta-cyclodextrin side-groups and a guest polymer with pending hydrophobic 4-tert-butylanilide side groups were synthesized by polymer-analogous reactions starting from poly[(maleic anhydride)-alt-(isobutene)] ((M) over bar(w), = 60000). The inclusions of both polymers with complementary monomeric guests and hosts are proven by microcalorimetry. The interaction of the host polymer and the guest polymer in aqueous solution is accompanied by a tremendous increase in viscosity.