Colloidal solutions of silver nanoparticles were prepared in water by ablation with 1064, 532, or 355 nm laser in order to investigate influences of laser wavelength on the particle size. Particles were characterized by using an electron microscope. The mean diameter of particles became smaller from 29 to 12 nm with decrease in laser wavelength under the irradiation of laser at a high fluence of 36 J/cm(2). It was explained in terms of fragmentation of colloidal particles by self-absorption of laser pulses. A quantitative disagreement of the efficiency of self-absorption on both the ablation efficiency and particle size with the absorption intensity of colloids was discussed on the basis of dynamic change in the morphology of colloids. (C) 2002 Elsevier Science B.V. All rights reserved.