3-Methyl-1,3-pentadiene was polymerized with the system Fe(bipy)(2)Cl-2-MAO (bipy = bipyridine) obtaining a highly stereoregular polymer. The polymer was completely characterized by IR, NMR (C-13, H-1 in solution and C-13 in the solid state), DSC, and X-ray techniques and found to have a syndiotactic E-1,2 structure. The crystalline structure of the polymer was also determined, and comparisons are made with other crystalline 1,2-polydienes. The results were compared with those obtained from other dienes (butadiene, isoprene, 2,3-dimethyl-1,3-butadiene) with the same catalyst, which allowed for new data confirming and supporting what already proposed to interpret the diene polymerization mechanism.