This paper discusses the Australian Centre for International Agricultural Research (ACIAR) Economic Impact Model which can be used in ex-ante and ex-post evaluations of projects. The model is a traded good model which estimates changes in producer and consumer surplus as a result of a supply or demand shift. It is written in Microsoft® Excel 97 and uses Visual Basic macros. The model is part of the Impact Assessment Program’s long term aim of developing systematic user-friendly approaches for the evaluation of agricultural research projects. It includes modules to allow the user with the required data to estimate cost savings for each one of the following situations: • Supply shift for an annual crop • Supply shift for a perennial crop • Supply shift for livestock commodities • Supply shift for aquaculture • Supply shift due to changes in postharvest wastage rate cost • Demand shifts due to changes in product quality or consumer preference. The paper shows how the model can be used and mentions examples where the model has been used in project evaluations.