Tritium is a radioactive hydrogen isotope that is of interest for both civil and military applications. Most of tritium is used for the realisation and the maintenance of fission and fusion nuclear weapons while only a minor fraction of tritium is commercially used. Among the non-military uses; medical diagnostic and research in pharmaceutical laboratories are discussed. For research purposes, tritium is also used in fusion power machines and, in particular, the development of processes for tritium recovery in the fusion fuel cycle has been the object of significant technological improvements. This book provides an overview on the processes for the production and treatment of tritium in nuclear fusion machines as well as the aspects of measurement, dose assessment and safety of tritium with a focus on the impact to human health and the environment.