Forests continue to fall for agricultural purposes throughout the humid tropics, with immediate and potentially large consequences for climate change and biodiversity loss-issues of key interest to the international community. Some of the actors directly responsible for forest conversion fell trees to meet food security needs and alleviate poverty-issues of urgent inte~est to them and also to national policymakers. This multiplicity of groups with differing (often conflicting) interests in the multifarious goods and services produced by tropical forests complicates the search for alternative agricultural activities for forest margins since these alternatives must satisfy such divergent objectives. This paper sets out a conceptual framework for comparing the impacts of different land use systems and agricultural practices at the margins of tropical rainforests in terms of the concerns and objectives of two key interest groups: small-scale farmers seeking livelihoods at the forest margins and the 'international' interests in the global public goods and services supplied by tropical rainforests. This framework should be useful to a third key group, the national and regional policymakers who must consider these and other policy objectives and then decide on courses of action. The paper identifies data needs and analytical methods capable of supplying an empirical base for this conceptual framework, based on quantifiable indicators. It then presents preliminary results of the application of this conceptual framework in Indonesia and Brazil in association with a global, collaborative, multidisciplinary research program. Even using preliminary order-of-magnitude estimates (to be replaced by more precise measurements as they become available), this conceptual framework presents results in ways that allow researchers and policymakers to select clear 'best bets' for development, when they exist, and to assess tradeoffs and options for complementary policy action and research efforts, when they do not. © 1998 Elsevier Science B.V. All rights reserved.