Recent reviews of the transfer of radiocaesium to ruminants after the Chernobyl accident (Howard 1989; Ward & Johnson 1989) have shown that there are a number of animal and dietary factors which may affect the transfer of radiocaesium. However, there is insufficient information available on the importance of these factors to enable predictive models to take them into account. Similarly, few attempts have been made to understand the relationship between radiocaesium levels in animal feed and tissues in terms of metabolic processes and mechanisms. Such an understanding may help to improve the effectiveness of countermeasures applied after releases of nuclear material to the environment. This paper describes a multinational research programme, funded for 2 years (1990/1991) by DGXII of the CEC, which intends to study some of these factors. The participants work in 10 laboratories in seven different countries spread throughout western Europe and Scandinavia.