A mass transfer correlation for distillation using a laboratory size wire-gauze structured packing was developed in terms of dimensionless diffusion flux based on experimental data for an acetone-ethanol system under total reflux conditions, The theoretical basis for mass and heat transfer in distillation that was previously developed for wetted-wall columns is shown to apply to structured packings as well. It is also demonstrated that the Sherwood number for distillation exhibited wide scattering due to the effect of convective flux, which is highly influenced by external heat effects and differences in the latent heat of vaporization of the transferring components. The model obtained from the binary system, which is based on the total area of the structured packing and corrected for the effect of condensation of mixed vapors, is shown to apply to a ternary system of acetone-methanol-ethanol. Simulation results using the correlation for a short column compared well with experimental results for longer columns for binary and ternary systems.