The heath effects of low-dose ionizing radiation have been widely studied, but uncertainty remains. To provide insight for national radiation protection policies, a multidisciplinary team of research, on behalf of the Italian Institute of Social Medicine, made a comprehensive search of the epidemiological evidence on the argument, published since July 2003. After the exclusion of updated cohorts, 302 papers were reviewed and data extracted. More emphasis was given to SIR/SMR estimates (external comparisons) as well as to studies on health personnel, aircrew members and all workers exposed, according to national working patterns. However, also data on A-bomb survivors, Chernobyl cleanup workers, exposed to medical irradiation and nuclear workers were considered. Taking into account the limitations of the epidemiological approach and excluding cosmic rays context, which requires further research, authors conclude that harmful effects of doses lower than 100 mSv cannot be ruled out; however, these effects, if any, are very small, and concerns from the LNT model should be scaled down. The implications for radiation protection, public health and legal medicine are discussed.