Proceedings of a symposium, Vienna, 8-12 May 1995. This was the first major IAEA meeting for more than a decade dealing specifically with the transfer of radionuclides in the environment. Its purpose was to review the information that has become available in recent years, notably as a result of the Chernobyl accident but also gained from studies of the discharges from civil and military nuclear facilities in the early nuclear age. This information has been used for improving the reliability of environmental model predictions, and the main results of the IAEA/CEC programme on Validation of Environmental Model Predictions (VAMP) were presented. In addition, progress in the IAEA programme on the International Arctic Seas Assessment Project (IASAP) was summarized.