In this paper, we report a simple chemical reduction method for synthesis of spherical Ag nanoparticles (average size similar to 7 nm) within mesoporous alumina matrix. Shape and size of the Ag nanoparticles and structure of the catalysts are investigated by using high resolution transmission electron microscopy, diffuse reflectance spectroscopy, N-2 adsorption-desorption analysis, XRD and particle size analysis. The synthesized catalysts possess BET surface area of 281.6 m(2)/g and average pore size 638 nm. The synthesized Ag nanoparticle loaded mesoporous aluminas exhibit catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol. (c) 2012 Elsevier B.V. All rights reserved.