Abstract During the last years, gas assisted injection moulding has been implanted in lots of applications [1] , [5] , which are usually quite different between them. The quality is highly improved for lots of parts, and so, many manufacturers think of this process to solve any kind of problem. In order to be able to apply a gas technique to a part, this one must have some characteristics that make it susceptible of applying gas assisted injection moulding, and obtain satisfactory results. According to TIIP experience, [3] , [4] gas assisted processes can be usually divided into three different techniques: conventional gas assisted technique, rib emptiness technique without overflow pipes, and rib emptiness technique with overflow pipes. In this paper, an overview on these three techniques will be done, taking into account the kind of parts on which each technique should be applied, and showing their advantages and disadvantages. The TIIP, where this study has taken place, has a great knowledge on plastics and its transformation, and it owns a great infrastructure that has allowed them to carry out all the stages of this study: at the first stage, a theoretical analysis by using the CAD–CAE software C-MOLD [2] , and at the second stage, testing and stating exactly the results previously obtained, in its test laboratory.