Energy transfer in thin films of zinc tetra(-octylphenyl)-porphyrin (ZnTOPP) doped with the copper (CuTOPP) or free-base (H2TOPP) analogues were investigated by time-resolved fluorescence and Monte Carlo simulations, applied to a single domain model of parallel porphyrin stacks. Rate constants for intra- and inter-stack energy transfer are (0.8-1.1) x 10(12) and (71-91) x 10(9) s(-1), respectively. The fluorescence lifetimes for ZnTOPP and H2TOPP films are (1.80-1.88) x 10(-9) and (6.8-7.3) x 10(-9) s. The rate constant for H2TOPP to ZnTOPP back transfer is (8.8-9.4) x 10(6) s(-1). The results agree with those of a previous analytical analysis [1].