Radon is a naturally occurring radioactive noble gas that has variable distribution in the geological environment, and is a decay product of uranium (and radium) that occurs in a wide range of rocks and soils. Indoor radon has been linked to 1000–2000 radon-induced lung cancer deaths in the UK each year (Darby et al., 2005). This project builds on previous work published by the authors (see Phillips et al., 2004; Groves-Kirkby et al., 2006) on long-term versus short-term radon testing in UK domestic properties for DEFRA (Phillips et al., 2004). This work was initiated in order to establish if short-term testing (for example, using 7-day activated charcoal detectors as advocated by the Radon Council in the UK) could be a way forward for the UK housing market (in other words, testing at time of conveyancing) or whether the established methodology recommended by the NRPB (now the HPA) of a minimum of three month testing using track-etch methods (and subsequent estimations of a year’s dose again using current protocols) was still appropriate