All studies concerned with jet mixing have been focused on liquid phase systems and no studies have been found on jet mixing for gas-liquid two phase systems. In the present study the use of jet fluid as a mixer in gas-liquid systems was proposed. Further by installing an experimental setup, the mixing behavior of liquid phase was studied. Gas flow and jet flow are injected to the mixing vessel countercurrently. In this study, the effect of jet injection, location of the conductivity probe, aeration rate and jet Reynolds number on the mixing time are investigated. The created flow pattern was extracted for each condition and the results often analyzed on the basis of them. It is observed that, for low aeration rates, the injection of jet decreases the mixing time considerably. By increasing the aeration rate, the difference in mixing times between the two cases of jet injection and without jet is reduced. Results also show that the closer the probe is to encounter location of the jet and airflow, the lower the mixing time obtained. Dependence of mixing time on the probe location decreases by increasing the mixing intensity and eliminating dead zones. It is obtained, on the basis of Re-j and the amount of jet travelling in the vessel, increasing the aeration rate has different effects on the performance of mixing. Generally, four different trends for the variation of mixing time with increasing the aeration rate are observed. Crown Copyright (C) 2010 Published by Elsevier B.V. on behalf of The Institution of Chemical Engineers. All rights reserved.