Abstract: The mathematical correlations are presented for taking into account the effect of entrainment on distillation tray efficiency under the conditions of no mixing of the vapor and partial mixing of the liquid. The calculated results are in good agreement with that of numerical solutions reported by Lockett et al. The mean error is 1.53% for liquid flowing in the same direction on each tray and 0.73% for liquid flowing in the opposite direction on successive trays. The analytical solutions obtained in this paper are more convenient to use.