The two-photon absorption (TPA) properties of a series of symmetrical fluorene and carbazole derivatives have been studied to determine the role of the central core and the solvent polarity. The molecules bear triphenylamine, oxadiazole and pyrene as electron donating, electron acceptor and pi-conjugated edge substituents, respectively. Triphenylamine and pyrene substituents with fluorene-core as well as oxadiazole substituent with carbazole-core constitute the optimum selections for enhanced TPA properties. Studying the effect of the solvent polarity it is shown that maximum TPA cross-sections (as high as 1024 GM) are achieved in a solvent of intermediate polarity. (C)2007 Published by Elsevier B.V.