We report on the two-photon absorption (2PA) cross-section for eight azoaromatic compounds in dimethyl sulfoxide solutions, using the Z-scan technique with femtosecond laser pulses at 775 nm. The 2PA cross-sections of these molecules are of the order of (1-6) x 10(-50) cm(4) s photon(-1). A correlation was established between the molecular structure and the two-photon absorption process, which makes it possible to develop molecular design strategies to create structures with suitable two-photon absorption coefficients. (C) 2002 Elsevier Science B.V. All rights reserved.