This paper probes into the wide array of networks that shaped malaria control in the colonial Lagos during the nineteenth and twentieth centuries. It highlights the role of tropical locales in the production of medical knowledge, emphasizing the ways colonial doctors read and contributed to imperial discourses on tropical diseases. Existing histories suggest the existence of wide-ranging inclusive and complex circuits of knowledge production networks of European institutions and persons who ventured into the field of tropical medicine. Malaria research undertaken in Lagos between the 1890s and the early 1900s generated key ideas and findings that impacted on imperial medical science. Attempts to deal with malaria also created sites for contestations between the imperial blueprint that emphasized racial segregation as a disease control measure from the local view that regarded outright segregation as economically suicidal, advocating instead for environmental control.