Malaria's epidemiological importance in Mexico greatly exceeded that of hookworm, but the Rockefeller Foundation (RF) paid far more attention to hookworm. Although the RF collaborated with malaria campaigns around the world, malaria was only incidental to the RF's activities in Mexico. The hookworm campaign, on the other hand, involved the RF at every stage, from conceptualization and design to financing, hiring, and day-to-day administration. This paper seeks to understand why the RF's involvement in Mexico differed for the two diseases and what the organizational, political, and health implications were for these divergent approaches. Beginning in the mid 1920s the Mexican government developed a modest anti-larval service, periodically draining and filling ditches and swamps, dusting Paris green, petrolizing stagnant water, and administering quinine. Following the RF's 1927 shift towards scientific investigation, it began to sponsor small-scale malaria research, collecting climatological, entomological, epidemiological, and clinical information. The Mexican government eagerly petitioned the RF to join a national effort, but it was reluctant to become involved. A National Malaria Campaign was established in 1935 under President Lázaro Cárdenas to coordinate education, sanitary engineering, and treatment. The popular Campaign followed RF strategies even without its direct participation. Meanwhile, the RF avidly pursued modest malaria research in Mexico, funding U.S. investigators to conduct experiments on pesticides, mosquito-trapping, and controversially, watering methods for rice. These efforts culminated in the world's first field trial of DDT against louse-borne typhus and later as a residual spray for malaria. In the end the RF used Mexico as a convenient locale for scientific research that had global implications but only an incidental relationship to Mexico's own Malaria Campaign. Likewise, the RF's much more active hookworm program was more a means than an end, leading not to eradication of the disease, but to Mexico's commitment to modern public health organization and methods.