This chapter discusses Emil Kraepelin’s views on degeneration. Of the many contributing factors, two are considered by him decidedly ‘poisonous’ for individual and collective health (‘Volksgifte’): alcoholism and the transmission of venereal diseases, particularly syphilis. Kraepelin’s concerns with degeneration echoed those of many eugenicists, in Germany and elsewhere, who believed that modern civilisation had become increasingly antithetical to the improvement of the race. In the early twentieth century, alcoholism was considered a ‘disease’ by many medical experts, including by some prominent psychiatrists. This issue seemed all the more pressing in the light of the growing number of the so-called ‘degenerates’, who were institutionalised across Europe and the United States. Kraepelin was one of those psychiatrists who repeatedly emphasised alcohol’s degenerative effects on human heredity. ‘Degenerative psychosis’ (‘Entartungsirresein’), he argued, was hereditary and a threat to the race. To prevent it from spreading further, he called on the state to take decisive action, using medical and therapeutic means but also through the application of racial hygiene (‘Rassenhygiene’). Kraepelin’s scientific credibility assured that his views on degeneration were widely shared by other German psychiatrists. That many of them were also eugenicists is a sobering truth. Another uncomfortable truth is that much of psychiatry’s scientific authority was developed during this period of intense popularisation of racial sciences. Therefore, in order to understand Kraepelin’s engagement with the hereditarian theory of alcoholism and to explain his observations on degeneration, the historical context of early twentieth century eugenics needs to be studied more rigorously by both practitioners and historians of psychiatry.