Farmers operate within specific natural and socio-economic settings. When those settings are very diverse, as in mountainous areas, agricultural extension services have often failed to tailor interventions to the specific needs of client farmers. In such settings, extensionists need cost-efficient tools or a close link to researchers to evaluate potential strategies and activities to raise farmers' income. This need has become more critical as governments in developing countries downsize expenditure on extension services and donors demand impact from their investments. This paper outlines a flexible computer-based farm-household model designed to assist researchers, extension workers, and policy makers. The model allows the user to define specific production options and resource constraints under different socio-economic and biophysical settings. Model application in different regions has proven its flexibility to capture and analyze a variety of production systems. When used with site-related input data and effective dialogue on the results among researchers, extensionists, and farmers, the model can be a useful tool for participatory research and extension. © 2001 Elsevier Science Ltd. All rights reserved.