A two-step site transformation technique is presented to convert from living ring-opening metathesis polymerization (ROMP) to living anionic polymerization of unsaturated monomers. This method permits the synthesis of well-defined diblock copolymers of controllable molecular weight and narrow molecular weight distribution, combining ROMP and anionically polymerizable monomers. The technique employs a functional terminating agent to add a styryl group to the end of the ROMP chain. The end group is then metalated to yield an active site for anionic polymerization, so that the ROMP chain acts as a macroinitiator from which the anionic block is grown. Both polycyclopentene/polystyrene and polynorbomene/poly styrene diblocks were successfully synthesized, and the method should be applicable to a broad range of monomers.