Introduction Social science research into technology and sustainable development has broadened in recent years (Berkhout, 2002) as analysis has extended beyond the study of the development and diffusing of individual cleaner technologies. Increasingly, analysts are studying the transformation of entire sociotechnical regimes, and making recommendations for inducing and steering radical system innovations in more environmentally sustainable directions (Elzen et al, 2004; Loorbach and Rotmans, 2004; Schot et al, 1994). The aim of this paper is to introduce the literature on systems innovation, and to use a case study into organic food to test a critical element in that literature: namely, the degree to which niches have to be radical or compatible in order to influence sustainable systems innovation. Taking a sociotechnical perspective means that technical elements across a regime such as food provisionöphysical inputs, plant-breeding techniques, pesticides, harvesting technologies, animal husbandry, transport, food processing, cooking technology, and so onöare studied and understood in tight relation to social elements, such as prevailing attitudes towards the meaning and purpose of farming, ideas about soil health and nutritional food, official agricultural policy and price-support mechanisms, the structure of food retailing, shifting trends in food consumption, and other social considerations. It is the coevolution of these social and technical elements that determines the way the food regime operates. The analytical challenge is to understand the transformation of these sociotechnical regimes (Geels, 2004; Rip and Kemp, 1998). The systems-innovation literature considers niche initiatives as sources of radical innovation that have the potential, if managed strategically, to seed sustainable regime transformations (Kemp et al, 1998). Strategic niche management is advocated as a key policy approach (Hoogma et al, 2002; Schot et al, 1994). Strategic niches provide protected spaces in which alternative sociotechnical practices can be experimented with and developed in such a way that they subsequently inform and influence mainstream transformation. In its Fourth National Environmental Policy Plan, the Dutch