SUMMARY The National Blood Transfusion Service ( NBTS) in England and Wales was established as a single entity in 1946 and operated as such for almost half a century. During those 50 years, the blood service in Wales, as in the rest of the UK, saw many technological and operational changes. The automation of donation testing, the introduction of successive layers of microbiological screening, the creation of the Tissue Typing Laboratory (later renamed the Welsh Transplantation and Immunogenetics Laboratory) and the development of information technology brought - over a relatively long period - highly significant improvements to an organisation that had begun life as an Emergency Medical Service. Differing funding and reporting arrangements for the Welsh and English blood services made little difference in practice, but the devolution of government following the 1997 referendum in Wales would have a profound influence. Four years before the Government of Wales Act (1998) was passed through the UK parliament, the National Blood Authority ( NBA) assumed executive control of the English blood services but not the blood service in Wales. The Scottish National Blood Transfusion Service and the Northern Ireland Blood Transfusion Service had been created as independent organisations in 1946; thus, the scene was set for diversification between the four independent blood services, each operating in different political environments with different funding streams. The creation of the UK Blood Services Forum and its Joint Professional Advisory Committee in 1999 has, however, ensured consistency in professional matters. The blood transfusion service in Wales, in its new headquarters in Talbot Green, became known as the Welsh Blood Service ( WBS), or Gwasanaeth Gwaed Cymru in Welsh, reporting for most of its life to the Velindre NHS Trust, part of NHS Wales. Considerable changes would impact the WBS in the 21st century. Social changes would mean that the role of recruitment and marketing would become ever more important, although the impact of this was lessened somewhat by a decreasing demand for blood following the Better Blood Transfusion initiatives. The Medicines and Healthcare Products Regulatory Agency found new powers and impetus after the so-called EU Blood Directive was transposed into British law, and the inspection regime became significantly more onerous, requiring more resources to be put in this area. A strategic review found that some parts of the service required extensive modernisation, such as the information technology system in use and the deployment of staff on the blood collection teams, and these matters were attended to. The review also prompted the Welsh Government to consider the question of blood supply to and blood collection in North Wales, which had been the remit of the Liverpool Centre since the establishment of the NBTS in 1946. The Welsh Government duly announced the creation of an all-Wales Blood Service, and finally, in May 2016, 70 years after its creation, the WBS took over responsibility for blood collection and blood provision in the whole of Wales. [ABSTRACT FROM AUTHOR]