ZnSe/SiO2 nanocomposites were synthesized by sol-gel process. The X-ray diffraction and optical absorption spectra indicate that the samples were composed of ZnSe nanocrystals embedded in silica matrix. The nonlinear absorption was investigated using a single Gaussian beam of Nd:YAG laser (532 nm). Two-photon absorption coefficients were measured by the open aperture z-scan technique. As the input intensity increases, the higher-order nonlinear absorption and photodarkening effect were observed, and the transmittance showed the different features in different regions. (C) 2004 Published by Elsevier B.V.