The kinetics of the two-photon ionization (TPI) of N, N, N', N'-tetramethylbenzidine (TMB) in CH2Cl2-doped solid argon using 313 nm Hg lamp radiation is investigated by means of ultraviolet/visible (UV/VIS) absorption spectroscopy. The experimental findings can be quantitatively understood on the basis of a rate equation model. The ionization cross-section of TMB in the lowest triplet state and the rate constant of cation-electron recombination are obtained by adapting calculated to measured irradiation time-dependent concentrations of the cation.