Knowledge of health risks from chronic or repeated exposures to low-LET radiation with organ doses on the order of 100 mGy or less is of central importance for radiation protection and the safe use of ionizing radiation in medical diagnosis. While it is not yet clear whether the incidence of circulatory diseases is increased after such exposures, there is evidence of an overall elevated risk of cancer. QuantiWcation of site-speciWc cancer risks and their dependences on exposure patterns, age and other factors still needs clariWcation. It can be anticipated that approaches to resolve these questions will involve integration of mechanistic and epidemiological methods. The International Conference on Late Health EVects of Ionizing Radiation which was held in Washington, DC, 4–6 May 2009, was organized to stimulate such interdisciplinary research approaches. This volume includes nine papers based on conference presentations. Recently, radiation-induced genomic instability has been related to cancer incidence in an epidemiological study (Eidemuller et al. 2009). In this volume, StreVer reviews the evidence for the involvement of genomic instability in carcinogenesis and concludes that genetic predisposition for increased radiosensitivity is related to increased genomic instability and cancer predisposition (StreVer 2010). Genomic instability is often assumed to be an early stage in the carcinogenic process. A late step is the progression during which malignant cells develop into clinical symptomatic cancer. In a number of organs, especially thyroid and prostate, dormant or slow-growing tumours often do not develop into clinically relevant tumours. It is an open question how these tumours should be evaluated in assessing cancer risk and latency period. An approach is proposed by Fakir et al. (2010), who address this problem using lung cancer as an example. They developed a mathematical model that takes into account experimental, epidemiological and clinical data to predict latency period and conclude that radiation may be involved in progression from a dormant tumour to a clinically relevant one. Besides mechanistic understanding, precise dosimetry is important in estimating the health impact of radiation exposures. The large amount of autopsy data from Mayak workers is an important source of information on the biokinetics of inhaled plutonium in airways, the deeper lung, and other organs. In one of the conference presentations, Birchall et al. (2010) described how the Mayak autopsy data on lung tissue clearance and retention rates can impact on current International Commission on Radiological Protection (ICRP) biokinetic models of the respiratory tract. Another area where progress in dosimetry can improve epidemiological studies is computational phantoms. Bolch et al. (2010) review emerging techniques for constructing patientspeciWc phantoms, which are expected to become the basis of a new generation of dose reconstruction methods. Recent studies provide some evidence that leukaemia rates are increased after chronic exposures to low-LET radiation with bone marrow doses of approximately 100 mGy. Whether chronic lymphatic leukaemia (CLL) is associated with exposure to ionizing radiation, however, is not clear. Krestinina et al. (2010) present new data on this question. Leukaemia rates among about 30,000 Techa P. Jacob (&) Helmholtz Zentrum Munchen, German Research Center for Environmental Health, Institute of Radiation Protection, 85764 Neuherberg, Germany e-mail: jacob@helmholtz-muenchen.de; jacob@gsf.de