Constant amplitude fatigue tests, using a rig constructed from military Heavy Girder Bridge (HGB) components, has enabled a comparison to be made between full size welded and pin jointed details with relevant design curves. BS 5400, 7680 and ISDU 82022 curves were compared with the results and found to be realistic but safe. However, the categorisation of the details compared with the BS classification was not found to be easy and determination of the appropriate stress ranges required considerable care. Low prior overloads had no clearly determined effect on life.