An upper-rim-substituted calixarene tetracarboxylic acid forms hydrogen-bonded duplexes with lower-rim-substituted tetra(4-pyridyl)- and tetra(3-pyridyl)calixarenes in chloroform. The formation of these adducts was studied by extraction experiments. The association constants determined via1H NMR dilution experiments in CDCl3 are 7.6 × 103 and 1.3 × 103 M-1 for the 4-pyridyl and the 3-pyridyl derivative, respectively. IR studies in the solid state and in solution indicate that the interaction is based on hydrogen bonding and that the degree of proton transfer is negligible. VPO measurements support the formation of 1:1 adducts.