The optical limiting properties of two polymer-bound multi-walled carbon nanotubes (MNWTs), poly(N-vinylcarbazole)-MWNTs (PVK-MWNTs) and polybutadiene-MWNTs (PB-MWNTs), were investigated using 532 nm nanosecond laser pulses. Both of them, especially PVK-MWNTs, showed much better optical limiting performance than that of C-60 in toluene solution. A nonlinear absorption mechanism was proposed and explanation was given on the interesting difference of the optical limiting properties of these two soluble MWNTs. (C) 2003 Elsevier B.V. All rights reserved.