Highly efficient, one-pot, four-component synthesis of 1,2,4,5-tetrasubstituted imidazoles was reported the condensation of various aldehydes, benzil, aliphatic or aromatic primary amines and ammonium acetate under solvent free conditions using perchloric acid adsorbed on silica gel (HClO4-SiO2) as catalyst in excellent yields. HClO4-SiO2 exhibited remarkable catalytic activity with respect to the reaction time (2-20 min), amount of catalyst. Present protocol with HC104-SiO2 catalyst is convincingly superior to the recently reported catalytic methods. (c) 2006 Elsevier B.V. All rights reserved.