Initiation of the polymerization of dienes bearing allylic protons with metallic alkali metals were investigated. Addition of a tertiary amine into the solution resulted in the complete inhibition of the polymerization to give a mono- or dianionic dienylmetal compound and reduced dimers in quantitative yield. The planar conformations of the isolated dienyl alkali metal compounds, which are considered to be real active species toward the alkali-metal catalyzed polymerizations, were determined by PMR and13C NMR spectroscopy. The catalytic activity toward polymerization as well as the chemical reactivity of those dienyl alkali metals was investigated.