An efficient and facile method for the synthesis of 3-[2-(2,4- dinitrophenyl)hydrazinyl]-2-benzofuran-1(3H)-one in a single step and very good yield (86%) by condensation of ophthalaldehydic acid and 2,4-dinitrophenylhydrazine using a polar solvent (methanol) at room temperature, The reaction occurred selectivity at carbon no.3 of the lactol form of the ophthalaldehydic acid acid. None of the Schiff bases of type (B) and cyclic product of type (C) have been formed. Thestructure of the product was confirmed from their spectral data (1H-NMR, 13C-NMR, and IR) and analytical data.