Programs to distribute improved biomass stoves have traditionally been unsuccessful, despite enormous potential health and climate benefits. This research note helps explain the reasons for this by considering three main prerequisites for technology adoption by the poor. The first success factor is motivation on the part of customers to adopt the new product. When motivation does not exist initially, it must be created through education, social marketing, or improved design. The second essential component is that the product be affordable, be it through disposable income, financing, or subsidies. Finally, the success of a product is dependent on the level of user engagement necessary to take advantage of it. Improved cookstoves rank poorly on all three dimensions: their benefits are rarely valued highly by customers at the outset, they are expensive, and they require a significant change in lifestyle to be put into use. These three potential barriers to adoption are relevant to any product aimed at consumers at the "bottom of the pyramid" in income. They help explain why some products (for example, Coca-Cola and cell phones) have penetrated markets rapidly while others such as cookstoves have achieved very limited penetration.