A methodology for the optimisation of the countermeasures associated with the contamination of animal products was designed based on cost-benefit analysis. Results are discussed for the hypothetical deposition of radionuclides on 15 August, when pastures are fully developed in Korean agricultural conditions. A dynamic food chain model, DYNACON, was used to evaluate the effectiveness of the countermeasures for reducing the ingestion dose. The countermeasures considered were: (1) a ban on food consumption; and (2) the substitution of clean fodder. These are effective in reducing the ingestion dose as well as simple and easy to carry out in the first year after deposition. The net benefit of the countermeasures was quantitatively estimated in terms of avertable doses and monetary costs. The benefit depends on a variety of factors, such as radionuclide concentrations on the ground, starting time and duration of the countermeasures. It is obvious that a fast reaction after deposition is important in maximising the cost effectiveness of the countermeasures. In most cases, the substitution of clean fodder is more cost effective than a ban on food consumption. The methodology used in this study may serve as a basis for rapid decision-making on the introduction of countermeasures relating to the contamination of animal products after a nuclear accident. (C) 1999 Elsevier Science Ltd. All rights reserved.