Due to Varied Flow Behavior, the Demarcation of Hydrodynamic Flow Regimes is an Important Task in the Design and Scale-Up of Bubble Column Reactors. This Article Reviews Most Hydrodynamic Studies Performed for Flow Regime Identification in Bubble Columns. It Begins with a Brief Introduction to Various Flow Regimes. the Second Section Examines Experimental Methods for Measurement of Flow Regime Transition. a Few Experimental Studies Are Presented in Detail, Followed by the Effect of Operating and Design Conditions on Flow Regime Transition. a Table Summarizes the Reported Experimental Studies, Along with their Operating and Design Conditions and Significant Conclusions. the Next Section Deals with the Current State of Transition Prediction, and Includes Purely Empirical Correlations, Semi-Empirical Models, Linear Stability Theory, and Computational Fluid Dynamics (CFD) based Studies. Copyright © 2007 the Berkeley Electronic Press. All Rights Reserved.