The European Commission has adopted a communication to assist Member States in transposing into national law Directive 96/29/Euratom, which lays down basic safety standards for the protection of the health of workers and the general public against the dangers arising from ionising radiation. The communication should serve as a reference document for Member States and offers guidance on the interpretation of certain provisions and definitions laid down in the Directive. The communication also clarifies the scope of the Directive, for example natural radiation sources which are essentially not controllable are not covered. However it is recognized that exposures involving natural radiation sources may be significant enough to warrant attention. Exposure to ionising radiation can lead to detrimental health effects in human beings and the Directive sets out the requirements designed for the protection of workers and the general public against these dangers, without unduly limiting the beneficial uses of the practices which give rise to radiation exposure. The Commission recognizes, in issuing this communication, that all those concerned with radiation protection have to make value judgements about the relative importance of different kinds of risks and about the balancing of risks and benefits. Guidance is therefore provided on issues such as quantities in dosimetry and radiation protection and the estimation of doses from external radiation sources. This is based on the most recent work of the International Commission on Radiation Units and Measurements (IRCU) and the International Commission on Radiological Protection (IRCP) reflecting the current status of scientific knowledge. Guidance is provided on the redefined values for the application of the requirements on reporting and on when authorization is needed for certain practices, including specially authorized exposures. The communication also provides clarification on dose limits that apply during normal operations and the dose limits that indicate when an intervention is required.