This article describes the synthesis and characterization of a series of homologous conjugated dimers and trimers bearing alkenyl moieties between furan and/or thiophene heterocycles, linked through their 2,5- positions, and a terminal aldehyde group. A tetramer was also isolated and characterized. These oligomers constitute (i) useful model compounds for the corresponding conjugated homo- and co-polymers, (ii) interesting molecular structures for electroluminescence and other optoelectronic applications, and (iii) potential precursors to more specific compounds (e.g. liquid crystals or photosensitive species) thanks to the terminal aldehyde function.