Medical developments in Latin America during the second half of the twentieth century have received little attention. This study examines the Mexican responses to the success and failures of an important international health campaign of the 1950s: malaria eradication. During the 1950s malaria became the disease of central concern for international and US agencies working in developing countries (as yellow fever and hookworm were for tropical health during the early twentieth century). This article outlines the motivations, design and techniques of the campaign. It concentrates on two local responses: first, the enthusiastic support displayed by personnel working in the field; and, secondly, the reactions against the campaign of a local doctor – who revealed some of the inadequacies of malaria eradication – and of two medical anthropologists, who emphasised the scant attention paid to the cultural and social aspects of the campaign.