Agricultural extension systems across Africa are under great pressure to become more efficient and effective. Whereas proposals abound as to what African governments should do in order to achieve these goals, those addressing how they might do so are rare. The literature still offers little guidance as to specific factors and processes that likely influence development and diffusion of agricultural technologies in given circumstances. This paper addresses this gap by analysing the outcome of a multi-year, farmer-centred intervention to control trypanosomosis a devastating livestock disease transmitted by tsetse flies carried out by the International Livestock Research Institute (ILRI) in South-West Ethiopia. While not conceived as such at the time, this intervention emerges, in retrospect, as a real-world experiment in decentralised private provision of a traditional public extension activity. The nature of the control technology and several biophysical and socio-economic characteristics of the region selected for control combined to produce a self-reinforcing process key to the success of the initiative. The intervention suggests that it is the demand-side of agricultural extension systems that matters the most, and that in most cases, an 'organised articulation of demand' will be required. The internal logic of that 'articulation' is the exact reverse of that driving privatisation and decentralisation of extension systems. That logic also differs significantly from that guiding 'demand-led, farmer-participatory' approaches to extension reform
