The extension of transplanted sorghum in northern Cameroon began in the 1950s and is now attaining remarkable proportions. It concerns from 150,000 to 200 000 ha throughout the plains in the extreme north according to the climatic conditions of the year. This spread has been caused mainly by the increase in food crop requirements resulting from population increase and also the development of cotton growing on land previously used for rainfed food crops. Studies have been performed at the local area ('terroir') level to gain a better understanding of the reasons for the phenomenon and its effects on farming systems. The spread can be as much as 200% in 20 years and is on vertisols and also seemingly less propitious vertic soils. It has been made possible by the perfecting of cultivation techniques and the endogenous dissemination of farming know-how, with an astonishing diversity of environments and varieties cultivated. Growers using the cropping system are encountering new constraints-especially weed growth- and are calling for external aid. An R&D programme initiated by the DPGT project (Développement Paysannal et Gestion des Terroirs) is leading to support services managed collectively by farmers' organisations.