In this work the sulfite oxidation (SOM), dynamic pressure-step (DPM) and gassing-out (GOM) methods were compared for volumetric mass transfer coefficient measurement in an airlift reactor with internal loop. As a liquid phase both, non-coalescent and coalescent media were used. Among the methods discussed here, the mass transfer coefficient (k(L)a) values obtained by the DPM appear as the most reliable as they were found to be independent of oxygen concentration in the inlet gas, which confirmed the physical correctness of this method. The difference between data measured using air and oxygen was not higher than 10%, which was comparable to the scatter of experimental data. It has been found that the sulfite oxidation method yielded k(L)a values only a little higher than those obtained by the DPM and the difference did not exceed 10%. Up to an inlet gas velocity (U-GC) of congruent to0.03 m s(-1) the GOM using oxygen as a gas medium gave k(L)a values in fact identical with those obtained by the DPM. At higher flows of the inlet gas, the GOM yielded k(L)a values as much as 15% lower. The enhancement in oxygen mass transfer rate determined in non-coalescent media was estimated to be up to +15%, when compared with a coalescent batch. The experimental dependence of k(L)a vs the overall gas hold-up was described by an empirical correlation.(1) (C) 2004 Society of Chemical Industry.