Stilbazolium derivatives are very attractive optical materials for photonics and biophotonics applications because a large number of these derivatives are available and they can exhibit large third-order nonlinear coefficients and rapid responses. To quantitatively characterize their third-order nonlinear coefficients and the temporal responses of their third-order nonlinear process, we have performed degenerate four-wave mixing and Z-scan experiments on four stilbazolium derivatives with different electron donors using 40 ps laser pulses at 532 nm. The y values for three of the compounds are on the order of 10-31 esu. These high values arise from electronic processes and are associated with both nonlinear absorption and nonlinear refraction. The relative contributions from nonlinear absorption and nonlinear refraction are dependent on the chemical structure and linear absorption of the stilbazolium derivative. © 2001 American Institute of Physics.