An efficient synthesis of 3,4- dihydropyrimidinones ( DHPMs) using bismuth ( III) nitrate as a catalyst for the first time from an aldehyde, beta- keto ester and urea in acetonitrile is described. Compared to the classical Biginelli reaction conditions, this new method consistently has the advantage of excellent yields ( 80- 93%) and short reaction time ( 1.5- 2.5 hours) at room temperature.