Venereal diseases (VD) have always been associated with the idea of sin, yet from the late 19th century, these pathologies gradually emerged und er a new light in western societies as a collective health threat, succe eding a long tradition in which venereal disease infection was merely se en as a self-inflicted punishment for committed vice. This historical-so ciological study explores the ways Belgian society dealt with sexually t ransmitted diseases, in particular syphilis and AIDS, as a public health problem in the period 1880-2000. As effective medical treatment covered only a small part of the period 1880-2000 - only after WWII could penic illin be used by doctors as a 'magic bullet' against sexually trans mitted diseases (STDs) -the public health campaigns against syphilis and AIDS were the major expressions of how Belgian society reacted to STDs in the late nineteenth and twentieth centuries. This study aims to make an original contribution to historical and socio logical research into public health in at least two ways. Firstly, it pr ovides a more complex and nuanced reading of the history of STD preventi on than the few studies that generally have drawn parallels between AIDS and former VD history in rudimentary, theoretically inaccurate and cont radictory ways. Secondly, it discusses the utility of the medicalisation thesis, which presents itself today as a hegemonic model in medical soc iological literature, for explaining the changing social reactions regar ding STDs over time. It is often assumed that the problem of STDs was su bject to a gradual process of medicalisation, in which initial, strong m oral beliefs regarding STDs in society gradually gave way to a more scie ntific and less moralistic approach to STDs. Following this thesis, the cultural status of STDs gradually moved from a physical punishment for c ommitted sin to an infectious disease that was included in preventive an d curative health care, like had been the case for other, less tabooed d iseases, in earlier times. However, a theoretical discussion of the medicalisation concept in Chapt er 1 reveals its conceptual limits. First of all, medicalisation theorie s are merely focused on the extension and growing influence of mainstrea m curative medicine, performed by legally certified physicians, excludin g alternative, more marginal types of medical knowledge and disease mode ls, or domains that are not concerned with the treatment of patients suc h as prevention and public health policy. Therefore, I adopted the socia l worlds/arenas model, developed by symbolic interactionists like Anselm Strauss and Adele Clarke, as a more flexible, conceptual device to map the variety of concerned parties, discourses and practices that were imp licated in the fight against STDs beyond the clinical setting. Another important drawback of medicalisation theories is that they generally pa y little attention to issues of individual agency and the regulation of the behaviour of larger populations in relation to the social fight agai nst diseases. Drawing on neo-Foucauldian literature on governmentality , I focused on the historical-specific ideas and strategies for governi ng the behaviours of populations and the self in relation to the proble m of STDs. In doing so, I was able to explore more thoroughly how the qu estion of STDs was connected with contemporary issues of public governme nt and sexual regulation. The historical evidence analysed in Chapters 2 to 9 reveals that what we today call STD 'prevention' significantly differed from how preven tion was conceived in earlier periods. In each of the three distinguishe d periods 1880-1914, 1914-1950, and 1982-2000 contemporary ideas and pra ctices with respect to STDs relied on distinctive explanatory medical-so cial theories on the biological and social conditions of STD transmissio n in society as well as on contemporary ideas about the best ways to int ervene in the targeted populations. Overviewing these different periods, it is clear that in the period of 1880-2000 the cultural definition of STDs changed from a physical punishment for committed sin to an infectio us disease. Yet, attributing this transformation to a progressive medica lisation of the problem of STDs would be a gross simplification. Instead , the observed shift should be understood as the result of interrelated changes in the domains of medicine, public health policy and sexual mora lity, which were articulated and negotiated at specific historical momen ts by committed social worlds in a contemporary arena. Three major evolu tions are crucial to understand this cultural transformation. Firstly, d octors could more easily and more exclusively define the STD problem in the public sphere over time, while at the same time, also other groups o f moral/social reformers and professionals were more eager to follow thi s medical definition. Secondly, explanatory theories of STD infection ha ve went through an enormous evolution in which the problem shifted from immoral 'types' of infected people to more abstract risk patterns o f behaviour in society as a whole. Concomitantly, public health measures against STDs individualised and became more comprehensive and fine-tune d over time, fundamentally switching from strategies of coercion to stra tegies of persuasion and education. Thirdly, changes in the public manag ement of STDs should also be understood against the backdrop of a progre ssing detraditionalisation of sexual regulation. Finally, I make a plea for the notion of the socialisation o f medicine as a better alternative for the medicalisation concept in or der to understand the observed social changes with respect to STDs. With this notion, the focus of analysis shifts from the biomedical model tha t is spread in an unaltered way as an ultimate, scientific truth in cont emporary society to the historically situated processes of translation through which medical notions with respect to STDs became useful in an increasing number of non-clinical, i.e. social settings.