STDs are inseparably related to prostitution. Yet the nature of this relationship is far more complex than is generally assumed because the issue is as much about actual medical problems as about social representations of the diseases. In Shanghai, the fear of the dangers of STDs in the late nineteenth century led a group of Western physicians in the foreign settlements to call for strict regulatory measures and for the medical control of the prostitutes by the authorities. Similarly, in the 1920s the transmission of STDs by prostitutes was a central element in the abolitionist campaign launched by the Moral Welfare League. 1 Finally, the Chinese authorities themselves adopted the same discourse after World War II to legitimize their attempt to establish a regulationist system in order to control prostitution and reduce the spread of STDs among the population. Chinese sources for the nineteenth century are almost completely silent on this topic, especially as they deal only with courtesans. The few references that exist are to be found in the medical journals published by missionaries. Because of their strong religious and moral tone and the lack of precise scientific techniques and instruments by which to identify STDs, however, these early testimonies can hardly be relied on. The following paper, therefore, will deal only with the period after the 1911 revolution. I shall briefly present the general position of prostitution and public health in China to avoid giving an unduly biased view of the Shanghai case. In this the measures adopted by the foreign and Chinese authorities in their more or less determined fight against STDs will feature prominently. The second part will examine the issue of STDs in relation to the role of physicians among the population and the prostitutes.