Experiments have been carried out in a 01 m internal diameter, 1.88 m height vertical Plexiglas column with an antenna type modified air sparger in the gas-liquid distributor section. This arrangement provides uniform mixing of the fluids, ensures the gas entering the fluidizing section as fine bubbles and reduces the pressure drop encountered through a conventional distributor used for the purpose The important dimensionless groups which have influence on the gas holdup have been developed by the use of Buckingham Pi theorem. The relation of gas holdup with these dimensionless groups has been expressed in the form of a power law equation developed with very high correlation coefficient Residual analysis has been carried out to validate the regression model The optimum operating conditions for maximum gas holdup in a co-current three-phase fluidized bed have been predicted using genetic algorithm. (C) 2009 Elsevier Ltd. All rights reserved