We investigate the intermolecular interaction effects on the static polarizabilities (alpha) and second hyperpolarizabilities (gamma) of hydrogen ( H)-bonded 4-pyridones, which have been recently found to produce extraordinarily strong H-bonds. The longitudinal alpha and gamma are calculated by the finite-field approach at the HF, MP2 and DFT levels of theory. The increase ratio of alpha per monomer for the increase of the number of monomers is found to be significantly enhanced compared to that of a per monomer. This feature suggests the presence of strong cooperative effects on gamma originating in the covalent interaction between polarizable pi-systems through H-bonds in the virtual excitation processes. (c) 2008 Elsevier B. V. All rights reserved.