Gas entrainment and holdup characteristics have been studied in a downflow bubble column with both Newtonian and non-Newtonian liquid. Aqueous CMC solutions at different concentration were used as a non-Newtonian and water as Newtonian liquid. In the present system, use of plunging liquid jet and ejector were synchronized to obtain significant entrainment and dispersion of gas into liquid. The effects of operating variables such as liquid flowrate, nozzle diameter, separator pressure, etc. on gas entrainment and holdup were investigated. Flow behaviours of non-Newtonian liquids were compared with that of Newtonian liquid. Furthermore, gas holdup data were analysed by slip velocity and drift flux model and found to be in good agreement with other reported results. The gas holdup of the present system was also correlated by some dimensionless groups of the independent parameters. (C) 2002 Elsevier Science B.V. All rights reserved.