The fibre/matrix interaction is a critical aspect of the composite behaviour for all composite families and has to be optimized for each new fibre/matrix system. In order to help this optimization, dedicated tests on model composites have been developed since fibre adhesion to organic matrices was first measured reproducibly in terms of bonding strength in the early sixties. Such tests provide a lot of information about the interface and related microphenomena and thus help to improve the materials. The progress is especially fast whenever the material is in an early stage of development. However, difficulties in the mechanical analysis of those apparently simple tests stand in the way of the introduction of relevant parameters into models of composite behaviour.