The World Bank began operations on June 25, 1946. Although it was established to finance European reconstruction after World War II, the bank today is a considerable force in the health, nutrition, and population (HNP) sector in developing countries. Indeed, it has evolved from having virtually no presence in global health to being the world's largest financial contributor to health-related projects, now committing more than $1 billion annually for new HNP projects. It is also one of the world's largest supporters in the fight against HIV/AIDS, with commitments of more than $1.6 billion over the past several years. I have mapped this transformation in the World Bank's role in global health, illustrating shifts in the bank's mission and financial orientation, as well as the broader changes in development theory and practice. Through a deepened understanding of the complexities of development, the World Bank now regards investments in HNP programs as fundamental to its role in the global economy.