Nanostructured composite of multi-walled carbon nanotubes (MWNTs) doped silica xerogel matrix was prepared by sol-gel technique. The successful encapsulation of MWNTs was checked by linear transmittance spectra and scanning electrical microscope images which show that MWNTs were well dispersed in the matrix. The optical limiting responses of MWNTs suspension and xerogel composite were observed at both 532 and 1064 nm with nanosecond laser pulses and shown to be good optical limiters. The optical limiting properties of MWNTs are maintained or even improved after being introduced into solid state matrix. The implying mechanism of nonlinear absorption other than the presently accepted nonlinear scattering is proposed and discussed. (C) 2003 Elsevier B.V. All rights reserved.