The first example of well-characterized main-chain type organoaluminum polymers was synthesized by polyaddition between dicyanobenzene derivatives and diisopropylaluminum hydride (DIBAL-H). As dicyano compounds, telephthalonitrile (1a), 1,4-didodecyloxy-2,5-dicyanobenzene (1b), 2,5-dicyanothiophene (1c), 4,4 0 -dicyanobiphenyl (1d), and 9,9-didodecyl-2,7-dicyanofluorene (1e) were used in the present hydroalumination polymerization. Among these compounds, 1b gave a comparatively stable polymer 2b. The molecular weight of 2b was estimated to be 2800 from gel permeation chromatography measurement. Because of its remaining instability for air and moisture, this molecular weight should be underestimated. The structures of the obtained polymers were confirmed by comparison with spectroscopic data of the model compound in 1 H and 13 C NMR.