This publication reports on the Third International Symposium on Protection of the Environment from Ionising Radiation, which focused on issues related to the development and application of a system of radiation protection for the environment. Topics covered include ongoing research on the effects, responses and mechanisms of the interactions of ionizing radiation with biota; policy and ethical dimensions of the development of a framework for environmental radiation protection; and the development and use of methods and models for evaluating radiation as a stressor to the environment.