Social, economical and environmental conditions of Urban Agriculture are very different between industrialized and developing countries, some research models and operational tools may be similarly questioned by this agriculture. In three case studies: in Senegal, France and Madagascar, where agro-economic surveys where done in punctual or long-term research programs, we question the renewal of the representation of farming systems' diversity, the duality of the concepts of sustainability and the analysis of multi-functionality of Urban Agriculture according to different actors. The global activity system must be taken into account due to the frequency of external activities to understand the agricultural production system itself. An external sustainability, i.e. the vision the urban planners and residents have about Urban Agriculture compared to other urban uses of land, is as important as the classical internal sustainability of farming systems to diagnose the future of urban agriculture. The place the urban planners give to agriculture in urban projects depends on the functions they or the inhabitants recognize to it. Thus, research must analyse them and lighten the hierarchy of functions made by these different stakeholders. The analysis of multifunctionality of urban agriculture crossed with internal and external diagnosis of sustainability is an important tool to help urban decision-makers to consider agriculture in urban planning.