Since 1974 the National Radiological Protection Board (now the Radiation Protection Division of the Health Protection Agency) has produced reviews of the levels of exposure to ionising radiation in the UK, from sources of natural and artificial origin. The latest review (Watson et al 2005 Ionising Radiation Exposure of the UK Population: 2005 Review HPA-RPD-001 (Chilton: HPA-RPD)) in the series gives estimates of annual doses based predominantly on data collected for the years 2001-2003. The overall average annual dose is rounded to 2.7 mSv, and the average annual dose from natural radiation is found to be 2.2 mSv. The overall average annual dose is slightly increased over that found in the previous, 1999, review. This increase is mainly due to a larger contribution from medical irradiation.