Abstract: A new efficient method for the synthesis of soluble thermoplastic polymers of isoprene with softening points in the range from 73 to 160°C has been developed. The method consists in the cationic polymerization of isoprene in dichloromethane or toluene in the presence of catalytic systems based on triethylaluminum in combination with tert-butyl chloride, tert-butyl bromide, 2-chloro-2-methylbutane, or isopropyl chloride.