Experimental and numerical studies of a gas-liquid two-phase flow have been applied to a non-baffled laboratory-scale stirred tank reactor, mechanically agitated by a gas-inducing turbine. The dispersion of air as gas phase into isopropanol as liquid phase at room temperature under different stirrer speeds was investigated. The X-ray cone beam computed tomography (CBCT) measurements have been taken at five different stirrer speeds starting from 1000 rpm at which the gas inducement occurs for the given operating conditions. The considerable difficulties in acquiring the phase distribution due to beam hardening and radiation scattering effects have been overcome by developing a suitable measurement setup as well as by calibration and software correction methods to achieve high accuracy. The computational fluid dynamics analyses of the stirred tank reactor have been performed in 3D with CFX 10.0 numerical software. The simplified numerical setup of mono-dispersed bubbles, constant drag coefficient and the k-epsilon turbulence model was able to capture both the bubble induction and dispersion and the free surface vortex formation. Despite the assumed simplifications, the numerical predictions exhibit a good agreement with the experimental data. (c) 2007 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.