Different crystallization conditions were investigated for syndiotactic poly-1,2-(4-methyl-1,3-pentadiene) (P4MPD). The thermal crystallization is a slow process. At 60 degrees C long times are needed to induce the structural rearrangements. Much shorter times are necessary for oriented samples, so that strain-induced crystallization occurs in a few hours. Solvent-induced crystallization produces a crystalline phase having small and poorly ordered crystallites. The crystallization process enhances the properties of the polymer, increasing both the modulus and the strength.