The neutron diffraction technique has been used to investigate the longitudinal stresses in the adherend produced as a result of cure and due to the application of a tensile load in a single lap shear joint. A comparison has also been made between the stress distributions in loaded "aged" and "unaged" joints. The neutron diffraction technique is the only viable method of investigating these stresses within metal adherends and enables comparisons between predicted and measured stresses to be made. The results of these experiments cast doubt on some of the predictions from finite element modelling of adherend stress levels.