Abstract: The formation of a polyion complex precipitate was applied to molecular imprinting for the first time. Polyanion containing boronic acid units can sustain AMP by a boronate-cis-diol interaction. When this polyanion forms a polyion complex with polycation according to 1 : 1 cation-anion stoichiometry,the phosphate anionic charges introduced into the polyanion by the AMP complexation are also counted. Thus, after removal of AMP from the polyion complex a 'cleft' which has the memory for the AMP template is created. It was proved that this cleft shows high affinity with AMP. We also noticed that the removal and re-binding processes for AMP coincide with the swelling and deswelling phenomena of this polyion complex