Gas liquid mass-transfer enhancement due to the presence of a second dispersed liquid phase has been discussed in this paper. Both the overall volumetric mass-transfer coefficient from the gas to bulk liquid and the partition coefficient were calculated under non-steady-state conditions. The results showed that the enhancement factor increased with an increase of the partition coefficient and the volumetric mass-transfer coefficient K(L)a clearly increased when a second dispersed liquid phase was added, with a clear maximum at 3% of the dispersed-phase volume fraction. The influence of the dispersed phase on K(L)a markedly depended on the agitation rate, and a maximum K(L)a was attained between 650 and 700 rpm.