The poorer half of the world's people have long relied for their energy needs on woodfuels. Since the oil shocks of the 1970s, pressure on forest resources has increased and the costs of traditional use of woodfuels have been growing—to the householder, in cash or collection time, and to society in inefficient energy use, deforestation, and local and global harm to health and the environment. Modern, efficient stoves can alleviate some of these problems; programs to design and disseminate them would seem a worthwhile pursuit for development activity. But do such programs in fact warrant the investment? Why have so many failed to catch on as expected? The authors find that programs have been most successful when targeted to specific areas where woodfuel prices or collection times are high. Field testing, consumer surveys, and involvement of local artisans from the outset have been critical to the ultimate adoption of the stoves. With these elements in place, external support from governments and donors can be useful; lacking them, subsidies may succeed only in distributing stoves that ultimately molder away unused. This article's review of what makes for success and failure is instructive for the design of stove programs in particular, and of development projects that propagate improved methods and technologies in general.