As part of the International Arctic Seas Assessment Project (IASAP) of the International Atomic Energy Agency (IAEA), a working group was created to model the dispersal and transfer of radionuclides released from radioactive waste disposed of in the Kara Sea. The objectives of this group are: (1) development of realistic and reliable assessment models for the dispersal of radioactive contaminants both within, and from, the Arctic ocean; and (2) evaluation of the contributions of different transfer mechanisms to contaminant dispersal and hence, ultimately, to the risks to human health and environment. With regard to the first objective, the modelling work has been directed towards assessment of model reliability and asone aspect of this, a benchmarking exercise has been carried out. This paper briefly describes the benchmark scenario, the models developed and used, and discusses some of the benchmarking results. The role of the exercise within the modelling programme of IASAP will be discussed and future work described.