The purpose of this project is to evaluate environmental transport and dose calculational models employed in the assessment of the radiological impact of routine and accidental radioactive discharges. This includes the identification of these models, the evaluation of their conceptualization, simplifying assumptions, and data bases, the estimation of their uncertainties and, if possible, the recommendation of the models and parameters which are best suited to particular assessment situations. Where needs are identified, recommendations will also be made for further environmental and biomedical research.