This Technical Reports Series publication incorporates contemporary information and scientific knowledge on the behaviour of tritium in the environment. It directly addresses existing and future concerns relating to anthropogenic sources of tritium that arise from power generation using nuclear fission and fusion technologies, nuclear fuel cycle activities, industrial and medical applications, accidental and deliberate releases, as well as military activities. This publication is also intended to serve as a technical reference on the radioecology of tritium, addressing current societal needs and acting as a guide for specialists and members of the public in understanding future environmental impacts. The intended audience of this publication includes specialists in radioecology, as well as technical specialists and decision makers dealing with the assessment of the impact of radioactivity on humans and the environment.