Bupleurum rotundifolium is one of the rarest archaeophytes in Central Europe. In Poland it is considered an endangered species (EN category; Zając et al. 2009; Węgrzynek 2014; Kaźmierczakowa et al. 2016) but in some regions it is already extinct (Kącki et al. 2003; Jackowiak et al. 2007) or critically endangered (CR category; Nowak et al. 2008; Cwe ner et al. 2016). The paper presents the current distribution, population size and habitat conditions of B. rotundifolium in the Chęciny Hills (southern Poland). The paper is based on floristic studies done during the vegetative seasons of 2010–2015 and supplemented in 2016–2019. The recorded localities were assigned to squares (2.5 × 2.5 km) of the ATPOL grid system (Zając 1978). During the study, three localities of the species were found in the vicinity of Bolmin and Milechowy villages. It grows in cereal crops and fallows on stony, Jurassic rendzinas on sunny slopes or at top of hills. The number of observed populations was estimated at hundreds or even thousands of individuals. The populations are threatened by intensification of agricultural practices. It is necessary to support traditional methods of cultivation on calcareous soils in areas where B. rotundifolium occurs (Zając et al. 2009; Węgrzynek 2014).