This article examines Richard Pearson Strong’s (1872-1948) research on tropical diseases in the colonial Philippines. Because the United States belatedly joined the line of imperialism after laboratory medicine had been established, Strong’s tropical medicine in the colonial Philippines was based more on contemporary laboratory medicine than his colleagues in Europe. But his research methods showed heterogenous and hybrid characters. Although he identified etiological factors and conducted vaccine experiments in the laboratory, he also adopted such traditional methods as observation and classification of symptoms and pathoanatomic investigations, particularly when dealing with unknown diseases like malta fever. In addition, the efficacy of a vaccine had to be measured against other kinds of vaccines, and for this reason, Strong carried out a series of large-scale human experimentations to verify his research on the cholera vaccine. The accident of cholera vaccine experimentation in Bilibid prison in 1906 showed both the uncertainty of Strong’s tropical medicine and the politics of colonial Philippines. By examining Strong’s research, this paper suggests that the practices of tropical medicine in the early twentieth century could not be wholly characterized as those of laboratory medicine, and that the uncertainty of vaccines on tropical diseases compelled the practitioners to draw on medical and political resources outside the laboratory.