The 21st L H Gray Conference, organised by the L H Gray Trust with the Society for Radiological Protection, brought together international experts in radiobiology, epidemiology and risk assessment, and scientists involved in diagnostic and therapeutic radiation exposure. The meeting - held in Edinburgh, Scotland, on 4-6 June 2008 - aimed to raise awareness, educate and share knowledge of important issues in radiation protection. A distinguished group of speakers discussed topics that included (i) non-targeted effects of radiation, (ii) exposure to high natural background radiation, (iii) non-cancer effects in Japanese bomb survivors, (iv) lessons learnt from Chernobyl, (v) radiation in the workplace, (vi) biokinetic modelling, (vii) uncertainties in risk estimation, (viii) issues in diagnostic medical exposures, (ix) lessons leant from the polonium-210 incidence and (x) how the radiobiology/radiation oncology community is needed to help society prepare for potential future acts of radiation terrorism. The conference highlighted the importance, relevance and topicality of radiobiology today. © 2009 The British Institute of Radiology.