Abstract: Process for manufacturing block copolymers derived from predominantly styrene and predominantly isoprene, used in the form of an isoprene concentrate obtainable by contacting an isoprene concentrate, obtainable by removal of piperylene from a gasoline pyrrolysis fraction of hydrocarbons having 5 carbon atoms, with finely dispersed alkali metal and/or alkaline earth metal, and separating it from the free and bound metal, said process comprising at least the steps of polymerizing predominantly styrene monomer in an inert non-aromatic hydrocarbon solvent in the presence of a monofunctional organolithium initiator, adding predominantly isoprene monomer in the form of pretreated isoprene concentrate to the polymerization mixture, either adding a coupling agent to couple a predominant part of the living diblock copolymer or adding a second portion of predominantly styrene monomer, and adding a terminating agent.