Multi-walled carbon nanotubes (MWNTs) were solubilized in organic solvents by the reaction of a secondary amine with the carboxylic acid groups bound to nanotubes. The solubilized MWNTs exhibited good optical limiting performances in both 532 and 1064 nm nanosecond laser pulses, which indicating that the solubilized carbon nanotubes are candidates for potential broadband optical limiting materials. A possible mechanism for the observed effects is suggested. (C) 2002 Elsevier Science B.V. All rights reserved.