Cross the invisible line into the base of the economic pyramid in emerging markets and you enter a world of pitfalls. If a company embarks on an initiative that focuses solely on commercial gain, civil society and governments are likely to oppose it intensely, as the international water utility company Aguas del Tunari discovered in Bolivia. If a company tries to stay under the radar by keeping its base-of-the-pyramid operations small, profits are likely to be meager, as Procter & Gamble found out with its water-purification product in Latin America and Asia. Even if you focus mainly on social impact and consider profits secondary, the base of the pyramid is a risky place: Projects that fail to make money will eventually be relegated to companies’ corporate social responsibility departments, as Microsoft discovered.

A version of this article appeared in the June 2011 issue of Harvard Business Review.