The effective interdiffusion coefficients of zinc in commercial Al-Zn alloys are obtained within the temperature range 773 to 883 K under pressures from 0 to 0.41 GPa. From the temperature dependence of the effective interdiffusion coefficients, the activation energies for the 701, 703 and 705 alloys are evaluated to be 125, 124 and 127 kJ/mol respectively, and their pre-exponential factors are 3.0 x 10(-5), 4.0 X 10(-5) and 3.9 x 10(-5) m(2)/s respectively. The activation volumes, Delta V, for diffusion of zinc in the commercial Al-Zn alloy are 8.30 x 10(-6) and 8.60 x 10(-6) m(3)/mol at 823 and 883 K, respectively. The ratios of the activation volume to the molar volume of aluminum, Delta V/ V-0, are 0.83 at 823 K and 0.86 at 883 K. This means that the diffusion of zinc in the commercial Al-Zn alloys occurs predominantly by the monovacancy mechanism at 823 and 883 K.