International health cooperation was an invention of the twentieth century. Not bound by colonial strictures, proselytizing mandates, or military objectives—and enabled by advancements in medicine and public health, international relations, and worldwide scholarly exchange—cooperation between specialized health agencies and willing countries offered a new form of voluntary international interaction. Part diplomacy, part development aid, part propaganda, part cultural imperialism, part economic opportunism, part humanitarianism, part scientific competition, the new international health went beyond the narrow self-interest of imperial powers or the focused agreements on nomenclature or standardization that were forged in the late nineteenth century. Unlike the health-related projects of missionaries, international health cooperation operated along strictly official terms—invited by government authorities through carefully orchestrated agreements. Though health officers may well have believed in their endeavors as much as missionaries did, they were rewarded with a paycheck and a career, not salvation. Moreover, international health agencies fostered public institutions and ideologies rather than private pieties.

By the 1930s, the Rockefeller Foundation had acquired vast experience in health cooperation in Mexico and dozens of other settings. Through its permanent field-based staff and scientific emissaries around the world, the RF had disseminated public health ideologies, implemented technological breakthroughs, and demonstrated health administration practices in cooperating countries. The RF's campaigns and activities had helped to control several diseases, promoted individual hygiene measures, and supported the development of national public health institutions. The thousands of fellows trained by the IHD had served as dynamic translators of RF public health efforts, tailoring them to local ideas and circumstances.

Mexico was just one of many venues for RF health cooperation, yet the relationship is revealing of broader patterns owing to its thirty-year duration, the variety of activities it involved, and the sometimes politically charged atmosphere in which it took place. By no means did the RF's international health work entail an outright transfer of public health ideas, methods, and technologies; nor did the various actors in Mexico or other places simply absorb the new knowledge and practices as consistent with their interests and appetite for political power. Instead, the RF joined an array of parties that included government authorities, health officials, a spectrum of healers, peasants, and labor groups, and local politicians who shaped and were shaped by their involvement with the RF and with one another.