BACKGROUND: 'Traffic light' (red-yellow-green) maps are potentially powerful tools for 'at a glance' problem detection, for optimising resource allocation/reallocation, setting priorities, and targeting interventions to areas most in need. The maps can be also used for administrative area comparisons and performance monitoring over time. Interactive Web versions of the maps can be generated with many handy features to further empower organisations and decision makers. Methodological issues to consider when creating 'traffic light' maps include hue thresholding, data timeliness and stability of administrative boundaries. RESULTS: We used 'traffic light' maps to study the distribution of dentists per 1,000 population in all 304 English Primary Care Trusts (PCTs) and 22 Welsh Local Health Boards (LHBs) using datasets of dentist numbers per PCT (as at 31 December 2002) and LHB (as at 26 February 2004) from the Dental Practice Board, and 2001 Census population figures for PCTs and LHBs from the Office for National Statistics. The overall NHS dentists per 1,000 population figures for England (0.374) and Wales (0.359) are low compared to many other countries, with less than 0.3 dentist per 1,000 people available to 24.1% of the total population of England (81 PCTs or 26.6% of all PCTs) and 26.1% of the total population of Wales (6 LHBs or 27.3% of all LHBs). A general shortage of NHS dentists can be observed at a glance across England and Wales on all the 'traffic light' maps in our study, even on those using a more "tolerant" classification and an additional orange-yellow class. The distribution of NHS dentists in England and Wales was also found to be not uniform, with some PCTs/LHBs, especially those located in some of the deprived or less populated urban and rural communities, suffering significantly more shortage of dentists than others (see http://healthcybermap.org/PCT/dentists/). These results confirm recent media reports of a shortage of NHS dentists in various parts of England and Wales. CONCLUSION: Suitable programmes are urgently needed to increase the numbers of NHS dentists across England and Wales. We have included a set of recommendations to dental health policymakers and planners, in addition to ideas for further work.