Cheap and reusable task-specific ionic liquids that bear an alkanesulfonic acid group in an acyclic trialkylammonium cation were found to be effective catalysts for synthesizing 3,4-dihydropyrimidine-2-(1H)-ones via the one-pot three-component Biginelli reaction. The satisfactory results were obtained with good yields, short reaction time and simplicity in the experimental procedure. The catalysts could be recycled and reused six times without noticeably decrease in the catalytic activity. (C) 2007 Elsevier B.V. All rights reserved.