Gas hold-up and mass transfer were examined in a column with and without a draft tube. It was found that the introduction of a draft tube increases the gas hold-up but decreases the volumetric mass transfer coefficient in Newtonian fluid systems. For non-Newtonian fluid systems, both parameters were increased by the presence of the draft tube. Empirical correlations are proposed for the gas hold-up and the volumetric mass transfer coefficient in the bubble column with Newtonian and non-Newtonian fluid systems. The correlations are in general agreement with the data in this work and in the literature. They should be useful for design and scale-up purposes. It was also found that introduction of an ancillary impeller improves the mass transfer in non-Newtonian fluids due to the break-up of large bubbles.