Abstract: In this paper the determination of the degree of association of polybu-tadienyl lithium in toluene as solvent has been reported. The experimentalresults show that the average degree of association of polybutadienyl lithiumin toluene is equal or greater than 2 (when the initiator concentratonis>1?10^-3mol/l). The viscosity ratio is not found to be influenced by thevariation of shear velocity in viscolsimeter, when the degree of associationof polybutadienyl lithium is measured by viscosimetry.