On the basis of a large bank of published experimental results fdr eight different types of extraction columns, namely, rotating disk, asymmetric rotating disk, Kuhni, Wirz-II, pulsed perforated-plate, Karr reciprocating-plate, packed, and spray columns, a unified correlation for the prediction of dispersed-phase hold-up is presented. Analysis of data with and without mass transfer shows that the hold-up can be expressed in terms of the mechanical power dissipation, phase flow rates, physical properties, and column geometry. The limitations of previously published correlations with regard to their application and solution are demonstrated.