The foundations of all mobile telecommunications networks are embedded in the radio spectrum to which the network operators have licensed access - without such spectrum there is no mobile business. In the changing world environment for telecommunications, and particularly within the increasingly liberalised markers of Europe, spectrum availability has become one of the key factors influencing progress. The availability of mobile spectrum is therefore, quite understandably, the subject of very dynamic political, regulatory, technical and market forces. The BT Group, as a major UK user of spectrum for mobile and many other radio applications, remains proactive in securing and developing its spectrum interests. Furthermore, as BT increasingly seeks to explore overseas mobile (and indeed fixed) telecommunications markets, its understanding of the radio regulatory environment is being extended progressively to cover many other countries. This paper reviews recent and current developments in those areas of the spectrum of greatest interest to the mobile operator, and looks at the main issues that have an impact on the growth of mobile service frequency allocations. Background information on the way in which the spectrum is managed at the national, European and global levels is also provided.