Radiation enhanced diffusion in the intermetallic alloy Cu3Au was measured directly for the first time. Ni and Pd tracer impurities were used to probe the diffusion of atoms occupying Cu and Au sublattice site's, respectively. Measurements were performed temperatures both above and below the ordering temperature, of TC =390°C The ability to grow high quality Cu3Au films by MBE with buried marker layers in the form of either (Cu2Ni)Au or Cu3(AuPd), made these measurements possible. Under irradiation with 0.75MeV Ar+ ions, the diffusion of Ni is approximately equal to that of Pd above Tc, but smaller below Tc. In the absence of irradiation, the thermal diffusion coefficients reveal a similar trend. Activation energies for RED for the two species are similar both above and below Tc whereas, in absence of irradiation, the activation enthalpies below Tc are different. These results are interpreted on the basis of lattice order.