Abstract: The relationship between the reactivity of the polymerization of a conjugated diene initiated by butyl lithium and the transition energy as solvent polarity parameter was studied. According to the experimental data, we derived some semiquantitative relationships as follows: where ΔH+Ex- Eσ is a complex activation energy of butadiene polymerization in cyclohexane in the presence of a Lewis base as polar additive. 2. Eapp = 74.04-1.756ET, E = 48.35- 1.107ET where Eapp and E are apparent and real activation energies of butadiene plymerization in different solvents respectively. 3. ΔH1,2-1,4 = 23.79-0.717ET where ΔH1, 2-1,4 is the difference of activation energies of 1,2-and 1,4-structures formed during butadiene polymerization in different solvents. 4. Eapp = 97.62-2.409ET where Eapp is the apparent activation energy of anionic polymerization of isoprene in different solvents.