The present report provides a comprehensive overview of the release, control and monitoring of radon. lt complements Technical Reports Series No. 335, Current Practices for the Management and Confinement of Uranium Mill Tailings, which provides a general account of the siting, design and construction of tailings impoundments. Contents: Notation; 1. Introduction; 2. Purpose and scope; 3. Factors controlling radon releases; 4. Methods for calculating radon releases from uranium tailings piles; 5. Measurement of radon concentration and flux; 6. Conducting a radon monitoring programme; 7. Summary; Annex A: Mathematical development of radon diffusion equations; Annex B: Refined methods of radon flux calculation; References; Glossary.