Recently, geotextiles have been employed in permanent works with consequent long term requirements for their satisfactory performance. The need has grown, therefore, for testing which provides data for specifications, quality control and design purposes. This paper points out that geotextiles are a group of materials which have widely differing internal structural arrangements. In many cases they are highly compressible and confinement can significantly modify their properties, in particular their pore space, load-extension and surface friction properties. These properties control the basic functions of separation, filtration, drainage-in-the-plane and reinforcement. As the modifications induced by confinement vary with the level and nature of the confining material, distinction has been made between in-isolation and in-soil testing. Recently developed apparatuses and test methods for both test modes are described and typical data are given. The usefulness of these in-isolation and in-soil tests for specifications, quality control and design purposes are then identified.