We report a new photon-gated photochemical hole burning system involving a donor-acceptor electron transfer reaction in which the electron acceptor, i.e. a Cl atom, is directly bonded to the matrix polymer chain in each monomer unit, namely zinc tetratolyltetrabenzoporphine (ZnTTBP)/poly(chloromethylstyrene) (PCMS). The simultaneous irradiation by an Ar+ laser in conjunction with a dye laser forms holes 70 times more efficiently than irradiation by the dye laser alone for this ZnTTBP/PCMS system. The irradiation intensity dependence and the annealing temperature dependence of the hole depth for a one-colour hole suggest that the hole formation mechanism for the latter is a non-photochemical process in the PCMS. The quantum efficiency of hole formation by two-colour irradiation and the gating ratio in PCMS are much larger than those found for poly(vinyl chloride).