Aryl-3,4-dihydropyrimidinones were synthesized using microwave-assisted, solvent-free protocol of the Biginelli reaction. The simple method provides the title compounds in 78%-95% yields by the reaction of aromatic aldehydes with ethyl acetoacetate and urea/thiourea in the presence of a catalytic amount of conc. HCl. Lewis acids, such as ZnCl 2, SnCl 2, FeCl 3·6H 2O, and CuCl 2·2H 2O, were also found to be efficient catalysts for the synthesis of dihydropyrimidinones. Aryl-3,4-dihydropyrimidinones were synthesized using microwave-assisted, solvent-free protocol of the Biginelli reaction. The simple method provides the title compounds in 78% -95% yields by the reaction of aromatic aldehydes with ethyl acetoacetate and urea / thiourea in the presence of a catalytic amount of conc. HCl. Lewis acids, such as ZnCl 2, SnCl 2, FeCl 3 .6H 2 O, and CuCl 2 .2H 2O, were also found to be efficient catalysts for the synthesis of dihydropyrimidinones.