Peel tests are commonly used to investigate the strength of adhesive joints. In the mandrel peel test the curvature of the flexible tape within the zone of detachment is controlled by the radius of the mandrel and this, coupled with an energy balance approach. allows separate determinations of the energy terms associated with any plastic or inelastic deformation of the tape and the de-adhesion or peel energy. If. in addition. the force oil the mandrel is monitored then the position of the force vector within the separation or de-adhesion zone can be established. This. in turn. permits a closer comparison with predictions from a peel model which allows non-linear behaviour of both the tape and the adhesive layer. The model has been validated by peel tests oil cellulose. PVC. aluminium and Teflon tapes carried out at sufficiently low speeds for rate effects within the adhesive to be small. Both the measured values of the de-adhesion energy, which varied from 60 to 160 J/m(2). and the positions of the force vector within the de-adhesion zone correlated well with those predicted from load-extension tests oil samples of the tapes and bulk samples of similar polymeric adhesives carried out at similar rates of deformation.