A general model for the design and scale-up of bubble columns and airlift loop reactors requires the exact prediction of their flow structure. The deterministic and stochastic components of the liquid flow in these gas-liquid contactors have therefore been measured. With the aid of a newly developed measuring technique, the hot-film anemometry with triple split probes, the local mean velocities, the turbulence intensities and, for the first time in bubble-column reactors, Reynolds shear stresses were determined. On the basis of a large amount of experimental data, a hydrodynamic model for the radial profile of the mean axial liquid velocity and an empiricial correlation for the prediction of the turbulence intensities have been developed. The hydrodynamic model and the correlation are valid for various reactor geometries, gas an liquid flow rates, and various properties of the liquid