The objective of my article is to investigate how the West had strong interest in tropical diseases and developed tropical medicine and hygiene from the 1870s through the 1910s Its focus is to identify the geopolitical conditions in which the West constructed ‘tropical diseases’ to extend its imperial interests into non-Western tropical regions The article has several specific research tasks first I attempt to explore the way in which European people transformed their attitudes toward tropical diseases from the sixteenth century to the 1860s A variety of writings by European physicians are discussed the second part shows European change in its domestic sanitary situation in relation to its imperial interests in tropical regions Sanitary hygiene in metropole and colonies are not separate but interconnected third the paper illuminates how the West responded to the spread of ‘Asiatic cholera’ in the nineteenth century Cholera provides a typical example for the West to perceive Asian origin of tropical diseases finally the article demonstrates that hygienic governance of tropical diseases is the key to imperial dominion over colonies by taking the Panama Canal as an example Although several European countries such as Spain Britain Germany and France had strong imperial interests in the Panama Canal that might facilitate trade between the Atlantic and the Pacific they failed to occupy the canal because of their inability to control high prevalence of malaria and yellow fever Taking advantage of ‘tropical medicine ’ the United States succeeded in taking up the canal by eradicating tropical diseases in the canal It was owing to the scientific development of tropical hygiene and medicine that the West transformed its pessimistic into optimistic position about the colonization of tropical regions Tropical diseases became the geopolitical reference for Western conceptualization of Asia Africa Latin America and the Pacific.