Gas absorption or stripping can be carried out in various absorbers such as packed columns, bubble columns, spray tower, plate tower, venturi scrubber and etc.. Each of these absorbers has its own advantages and disadvantages, and can be selectively employed depending on the gas-liquid system used. Hollow fibre modules, as new gas absorption or stripping devices offer considerable advantages over the conventional processes mentioned. This article reviews the progress of the membrane based gas absorption or stripping processes. Mass transfer of gases through various hollow fibre membranes is presented. Some of the most important theoretical models for gas absorption or stripping in hollow fibre membrane modules are also reviewed. Finally, discussions on design equations and potential application of hollow fibre modules in some specific areas of gas absorption or stripping are made.