The Polish Eugenics Society, founded in 1915, wielded considerable influence in the founding years of the Polish Second Republic. Leading medical experts in the Society placed issues of venereal contamination and the expansion of public sex at the forefront of their concerns. Unlike similar movements in Western Europe and North America, however, Polish eugenicists rarely attacked ethnic or religious difference and the organization included several prominent assimilated Jewish doctors. This article looks at the roots of Polish eugenics in the context of late imperial East-Central Europe, showing how scientific experts used their heightened public stature to challenge the governing empires. It demonstrates the ways in which the movement sought to protect the upper classes while promoting sterilization of unworthy lower-class citizens. The piece argues that the Polish eugenics movement was more classist than racist and that its scientific vocabulary helped position the Polish nation, broadly conceived, as more progressive than the imperial states governing Polish territory.