The densities of the binary mixtures formed by 1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF4] with aromatic compound (benzaidehyde) have been determined over the full range of compositions at the temperature range from (298.15 to 313.15) K and at atmospheric pressure using a vibrating-tube densimeter (DMA4500). Excess molar volumes (V-m(E)) have been obtained from these experimental results, and been fitted by the fourth-order Redlich-Kister equation. In addition, partial molar volumes, apparent molar volumes, and partial molar volumes at infinite dilution have been calculated for each component. Our results show V-m(E) decreases slightly when temperature increases in the systems studied. The results have been interpreted in terms of ion-dipole interactions and structural factors of the ionic liquid and these organic molecular liquids. (C) 2009 Elsevier Ltd. All rights reserved.