In 1992, ASTM initiated a Round-Robin on Reconstitution (RRR) to contribute to review the ASTM E1253 Guide on Charpy reconstitution. The purpose of this RRR was to study the influence of parameters, such as the reconstitution technique, the insert length, the hammer tup geometry and the material. Ten laboratories participated in the RRR and performed Charpy reconstitution according to a pre-defined test matrix. Comparison of the absorbed energy and lateral expansion before and after reconstitution demonstrates that the loss due to reconstitution can be characterized by the combination of the welding method and the tup geometry used. In general, stud and upset-butt welding combined with the ASTM tup show the highest difference in energy whereas electron-beam welding with the ISO tup indicates the least. The variations among welding techniques and laboratories are also described. The recorded instrumented Charpy signals establish the load diagram that forms the basis of an enhanced surveillance methodology for plant life management. It is concluded that reconstitution does not affect any characteristic loads in the instrumented load-time traces.