Gold nanoparticle (AuNP) solution prepared by laser ablation in liquid (LAL) was irradiated by ns laser pulses to investigate the wavelength dependence on the size distribution of AuNPs and long-term stability of post-irradiated AuNP solutions. We have employed 266, 355, 532, and 1064 nm lasers for post-irradiation source and found considerable wavelength dependence in the size distribution and stability of laser-generated AuNPs. Post-irradiation at 355 nm was most effective to reduce the size distribution and to enhance the stability. The classical Derjaguin-Landau-Verwey-Overbeek theory was employed to explain the anomalous stability at 355 nm. (C) 2013 Elsevier B.V. All rights reserved.