In the year 2005 studies on the Staphylinidae assemblages inhabiting ant nests of 13 ant species in the vicinities of Le ajsk (the Sandomierska Lowland; UTM: EA87) were conducted. In total, 671 individuals of rovebeetles were collected, among which 88 Staphylinidae species were identified. The most numerous rove-beetle inhabiting the nests of the studied ant species was Thiasophila angulata. The characteristic feature of rove-beetle assemblages is superior share of myrmecophiles, despite the fact that with respect to the number of species they are in the minority. Gabrius splendidulus and Sepedophilus marshami were associated with the nests of the highest number of ant species. The best conditions for rovebeetles associated with ants are provided by moist and moulding tree trunks and nests in shape of mounds of pine needles where the highest numbers of species as well as specimens of the described beetles were caught relatively. The highest species similarity joins Staphylinidae occurring in the nests of Formica fusca and Myrmica ruginodis. Index of qualitative similarity of the examined rove-beetle assemblages was strictly connected with the structure and localization of inhabited ant nests. The dependence of relationship proximity among ants building the nests was not found. Seasonal dynamic of rove-beetle numbers showed two maxima (spring and autumn). Its course is in large part dependent on quantitative fluctuation of myrmecophilous species as well as migration of rove-beetles to wintering sites. Some relationships between ant and rove-beetles species that have not been unknown so far were observed. Among all of the recorded species 13 ones were distinguished with respect to their faunistics and as many as 73 have been discovered for the first time in the Sandomierska Lowland.