This Report discusses the current status of fusion welding technology for copper-based materials of major industrial importance. It is a subject which receives relatively scant attention in the literature when compared to most other industrial metals and alloys. Much useful data remains unpublished and unavailable to a wider public. While this report can in no way purport to rectify this situation totally, it is made as a contribution, hopefully useful, and based on some 25 years of field experience. The Report begins by briefly describing the materials under discussion, and their metallurgy as related to fusion welding. Compositional and property data are given in Appendix 1. Brief mention is then made of applicable welding processes, but a basic knowledge of the processes themselves is assumed. A more detailed discussion follows on current welding practice for each group of copper-base materials. Finally, mention is made of potential process developments likely to make a contribution to the copper alloy joining field. Literature references and suggested further reading are given separately at the end of the main text.