At the end of the 19th and the beginning of the 20th century, under the influence of Spencer’s evolutionism, Darwin’s theory of natural selection and Mendel’s laws of inheritance, categories of people were identified that allegedly prevented humanity and nations from progressing. Among them, certain races, classes and other categories stood out, such as prostitutes, alcoholics, syphilitics, epileptics, mentally ill, criminals and homosexuals, and doctors and other intellectuals tried to find mechanisms by which such categories would be prevented from reproducing. In that period, the human body was conceptualized as a focal point of social and biological inequalities, but also as a key factor for the political survival and strengthening of the nation. Croatian doctors adapted degenerationist and eugenic theories from Central and Western Europe to specific local circumstances. Until the end of the First World War, as in the work of public health pioneer Andrija Štampar in the interwar period, eugenics lived as an integral part of public health programs. The implicit assumption of almost the entire eugenic thought was the Lamarckist theory of the inheritance of acquired characteristics. According to the theorists of the time, the biological characteristics of developed peoples and races encouraged cultural achievements, which, in turn, improved hereditary traits through the mechanism of inheritance of acquired traits. Considering the poor health conditions in which the Croatian people lived, Croatian doctors logically adhered to the concept of “plasticity” of the human body, and optimism was expressed towards the possibility of ameliorating dire socioeconomic and hygienic circumstances in order to improve the biological material. From the end of the 1920s, a new generation of eugenicists appeared in Croatia, who no longer saw public health as a partner, but as an enemy of eugenics. Among them, the most prominent was the Slovenian biologist Boris Zarnik, who no longer imagined the human body as inherently powerful and which the environment stimulated or prevented in the expression of its power, but as a pre-determined combination of features in accordance with Mendel’s laws of inheritance. Despite great efforts to establish and popularize such “scientific” eugenics, Zarnik experienced fierce criticism and softened his views on races until the end of his career. Eugenic case studies from Central and Southeastern Europe have recently influenced a change in the understanding of eugenics in the sense that it does not have to include repressive methods of euthanasia, sterilization or marriage ban programs as necessary prerequisites, nor be based on Mendelism. On the other hand, the expansion of the definition of eugenics has simultaneously diluted it to the extent that many public health programs are casually ascribed eugenic motivation on the basis of rather flimsy evidence. I hope, therefore, that this lecture will stimulate a fruitful discussion about the questions of the definition and limits of eugenics in countries where there was no institutionalized eugenics legislation and practice.