Two-photon absorption behavior of dispersion of solid solution nanocrystals of ZnS-AgInS2 was investigated, the measured maximum two-photon absorption cross-section of this nanoparticle being 3900GM (1GM = 10(-50) cm(4) s photon(-1) mol(particle)(-1)) at 850 nm. The two-photon excited red photoluminescence was observed even by using a femtosecond fiber laser oscillating at 1030 nm.