ArgumentMoreau (2019) has raised concerns about the use of DNA data obtained from vulnerable populations, such as the Uighurs in China. We discuss another case, situated in Europe and with a research history dating back 100 years: genetic investigations of Roma. In our article, we focus on problems surrounding representativity in these studies. We claim that many of the circa 440 publications in our sample neglect the methodological and conceptual challenges of representativity. Moreover, authors do not account for problematic misrepresentations (...) of Roma resulting from the conceptual frameworks and sampling schemes they use. We question the representation of Roma as a “genetic isolate” and the underlying rationales, with a strong focus on sampling strategies. We discuss our results against the optimistic prognosis that the “new genetics” could help to overcome essentialist understandings of groups. (shrink)