The four billion global consumers at the base of the pyramid (BOP) - those earning less than two dollars a day - are increasingly recognized by the private sector as a major untapped market segment. The sanitation industry is no exception. Across sub-Saharan Africa, more than half of the population lives without access to minimum levels of improved sanitation. Beyond the reach of urban sewerage networks, most BOP families require self-funded, household-level sanitation solutions. While the needs of this vast market are often pigeonholed as a development issue to be dealt with by the public sector and non-governmental organizations (NGOs), it represents a sizable market opportunity for the private sector. This brief captures early experiences from the 'Selling Sanitation' initiative, a partnership between IFC and the World Bank's Water and Sanitation Program (WSP). Using a market transformation approach, Selling Sanitation is demonstrating strong potential to unlock new market opportunities and dramatically increase access to sanitation for low-income consumers.