AbstractThe acid rain problem is just one amongst many complex environmental issues that are facing policy-makers today. Analytical advice normally takes the form of large and expensive studies, expressed in written reports. The availability of powerful dedicated and interactive computers opens the possibility for the analysis to be represented as an interactive computer program. The computer has considerable potential to improve the quality of the analysis available to a policy-maker.This paper will report on the construction of a decision aid on a powerful personal computer for the British Government, to study the acid deposition problem. As well as describing the technical issues involved in this model, the paper discusses the potential for this approach to policy analysis.