Weeds are an emerging constraint on crop production, as a result of population pressure and more intensive use of cultivated land. A diagnostic study was carried out from June through August 2002 in the five agro-ecological zones of Benin (1) to identify the relative importance of weeds among major production constraints, (2) to better understand farmers’ perceptions of weed problems, and (3) to take cognizance of their reactions and the different actors involved in weed management technology development. The study also aimed at suggesting the development of weed management strategies that work and are acceptable under small-scale farmers’ conditions. Data were collected through semi-structured and unstructured group and/or individual interviews, and through participant observation, transect studies and weed identification during field visits. The results show considerable diversity in biophysical constraints and socio-economic conditions. Population density has led to high pressure on arable land, resulting in land degradation and weed problems. In all situations, pernicious (Imperata cylindrica, Cyperus spp., Commelina spp.) and parasitic (Striga spp.) weeds are difficult to eradicate, causing substantial food crop yield losses and threatening the livelihood of people. Land and labour shortage, low commodity prices and lack of credit were the main constraints hindering weed management. Causes, effects and consequences were analysed, taking into account the socio-economic context. The study’s findings with respect to weed management measures, and their adaptation and constraints in using them, suggest that effective and acceptable weed management strategies should be developed, taking into account both biological and social science perspectives with a focus on adding value to indigenous knowledge. Promising strategies for discovery learning about weed management were identified, in order to fostersustainable crop production in Benin.