This lecture covers interaction of radiation with matter. Emphasis is placed on dosimetry and hot atom chemistry. Resulting chemical reactions and effects are highlighted. Dosimetry is introduced and explored. Units of dosimetry are described. Dosimetry measurements are discussed and quality factors based on particle mass and charge are introduced. Introductory dose calculations are supplied. Radiation protection regulations and the definition of terms (ALI, DAC) are given, including levels for use in the UNLV Radiochemistry laboratories. A review of hot atom chemistry is given.