Two-photon absorption spectra in absolute cross-section values are presented for a number of octaethyl-, tetraphenyl-. and tetrabenzo-substituted porphyrins. In excitation spectral region of 710-810 nm, the two-photon absorption efficiency is resonantly enhanced due to nearby Q(0-0) one-photon transition. The cross-section value calculated directly from the ground- and excited-state absorption parameters in a single intermediate level approximation, agrees well with that measured in experiment. (C) 2002 Elsevier Science B.V. All rights reserved.