The UK NBS completed the introduction of universal leucodepletion in November 1999. This involved the implementation of new methods of production, testing and monitoring, the development of which is still ongoing. Whilst important lessons have been learnt, much remains to be achieved in respect of quality improvement through standardisation of procedures, processes and product modifications to improve safety/efficacy of therapeutic blood components. Since the introduction of universal leucodepletion, many changes in component production and testing have occurred. The primary goal of this report is to review the level of standardisation and harmonisation currently achieved for low leucocyte counting within the NBS and discuss remedial actions undertaken to improve the standard of blood component production and quality monitoring and to highlight some of the related issues which are currently being worked on. The following issues are discussed.