The flooding behavior of a pilot scale Hanson mixer-settler extraction column with seven stages has been investigated using three different liquid-liquid systems. The effects of agitation speed, phase flow rates, and interfacial tension on flooding velocities and holdup at flooding have been investigated and found to be significant. The experiments showed that flooding Occurred by phase inversion under the selected operating conditions. Two precise empirical correlations for flooding velocities and holdup at flooding are derived in terms of the operating variables, column geometry and physical properties of the liquid-liquid systems. (C) 2009 Elsevier B.V. All rights reserved.