Abstract: The flooding point and hold-up of the dispersed phase in an extraction column with reciprocating-sieve plates of 32 mm inside diameter and 1960 mm effective column height have been investigated under the following conditions: Percent perforation of the plates 40%, 53.5% and 63.7%, diameters of perforated holes 7.8, 9.0 and 9.8 mm, and distances between plates 20 and 40mm respectively. Experiments were carried out with three different liquid-liquid systems covering a rather wide range of physical properties. The relative velocity of the two phases passing through the perforations of the plates is considered in the present work to be related to the work done by the oscillating plates in the column on unit mass of liquid in unit time. Therefore the flooding velocity and hold-up in extraction column with reciprocating sieve plates should be related to A2F3 instead of AF as reported before, where A is the amplitude and F is the frequency of oscillation. Equations were developed as shown below to correlate the experimental data of flooding point and hold-up respectively: Usf=5.95 and Where Usf and Vdf are relative velocity and velocity of dispersed phase at flooding point respectively in cm/s;φf, fraction of hold-up of dispersed phase at flooding point; ε, fraction of opening of plates; σ, interfacial tension in dyn/cm; AP, density difference between phases in g/cm3; h, distance between plates in cm and μc, viscosity of continuous phase in g/cm