This guidebook explores the basics of the interaction of radiation with matter both from the physical and chemical aspects and the relation to biological effects. Calculations of absorbed doses and dose equivalent and ways to minimize exposure and optimization of radiation protection in light of the latest international recommenda-tions are discussed and examples are shown. Frequently used dosimeters, radiation detectors with an emphasis on TL and chemi-cal dosimeters and the dosimetry of fast neutron beams with spe-cial attention to medical uses in neutron therapy are discussed. The latest data on exposure resulting from natural and man-made sources in the environment is also covered.