The historical and recent distribution, ecology and phytosociology of perennial grass Beckmannia eruciformis was studied in Slovakia between 2002 and 2010. Altogether 22 natural and two secondary sites with presence of the species were found from published sources, herbaria and field research. Localities of its native occurrence have been concentrated in Eastern Slovakia (Východoslovenská nížina Lowland from the settlement of Streda nad Bodrogom to the villages of Pribeník and Biel). Secondary sites were found in Western Slovakia (Podunajská nížina Lowland; the surroundings of Sládkovičovo town and Jaslovské Bohunice village). The relatively massive reduction of Beckmannia eruciformis localities was recorded in the seventies and eighties of the last century; it was related to massive land reclamation and alterations in the water regime of river alluvia. Recently only seven localities were found. Permanent occurrence was confirmed only in two localities (Malý Horeš, Strážne). In those cases Beckmannia eruciformis has created relatively large populations including some thousands of individuals. All other recent occurrences were temporary (Streda nad Bodrogom, Keresztúr farmstead, Horešské lúky Nature Reserve, Veľký Horeš, Pribeník). Moreover, they were relatively poor in the number in individuals and are acutely threatened by anthropogenic changes of environmental conditions. According to our results and by applying the IUCN criteria, we propose to modify the threat category of the species from critically endangered (CR) to endangered (EN) in Slovakia. Occurrence of the association Beckmannietum eruciformis and the alliance Beckmannion eruciformis, was also not confirmed for Slovakia during our research. We believe that the association was not present in the past either. Recently, Beckmannia eruciformis was found in the stands of Oenanthion aquaticae (Phragmito-Magnocaricetea) and Potentillion anserinae (Molinio-Arrhenatheretea) in two localities (Malý Horeš, Strážne) during our study. The species composition of the mentioned alliances is fundamentally influenced by the ecological conditions of sites, mainly by water regime during the vegetation period. According to our knowledge, the most favourable conditions for Beckmannia eruciformis are the following: short-term and low floods in the spring, decrease of the water table at the beginning of summer and relatively high level of groundwater during next part of vegetation period. On the contrary, the species may not appear on the site in case of unfavourable weather conditions (dry years). Preteklo in današnjo razširjenost, ekologijo in fitocenologijo večletne trave Beckmannia eruciformis na Slovaškem smo preučevali med letoma 2002 in 2010. V objavljenih virih, herbarijih in s terenskimi raziskavami smo našli 22 naravnih in dve drugotni rastišči. Mesta naravnih rastišč so skoncentrirana v zahodnem delu Slovaške (Východoslovenská nížina od naselja Streda nad Bodrogom do vasi Pribeník in Biel). Sekundarna rastišča smo našli v zahodnem delu Slovaške (Podunajská nížina; okolica mesta Sládkovičovo in vasi Jaslovské Bohunice). Razmeroma množično upadanje nahajališč vrste Beckmannia eruciformis se je začelo v sedemdesetih in osemdesetih letih prejšnjega stoletja in je bilo povezano z velikimi izsuševanji in spremembami vodnega režima ob rečnih naplavinah. V zadnjem času smo našli samo še sedem rastišč. Stalno pojavljanje smo potrdili samo na dveh rastiščih (Malý Horeš, Strážne). V teh primerih se vrsta Beckmannia eruciformis pojavlja v razmeroma velikih populacijah z nekaj tisoč osebki. Vsa druga nahajališča so prehodna (Streda nad Bodrogom, farma Keresztúr, naravni rezervat Horešské lúky, Veľký Horeš, Pribeník). Poleg tega so tukaj populacije maloštevilne in so ogrožene zaradi človekovega spreminjanja rastiščnih razmer. V skladu z našimi rezultati in uporabo meril IUCN predlagamo spremembo kategorije od kritično ogrožene (CR) v ogroženo vrsto na Slovaškem. Pojavljana sestojev asociacije Beckmannietum eruciformis in zveze Beckmannion eruciformis na Slovaškem pa nismo potrdili. Menimo, da asociacija tudi v preteklosti ni bila prisotna. Vrsto Beckmannia eruciformis smo v naši raziskavi našli v sestojih zvez Oenanthion aquaticae (Phragmito-Magnocaricetea) in Potentillion anserinae (Molinio-Arrhenatheretea) na dveh rastiščih (Malý Horeš, Strážne). Na vrstno sestavo omenjenih zvez vplivajo ekološke razmere na rastiščih, predvsem vodni režim med vegetacijskim obdobjem. Najbolj ugodne razmere za vrsto Beckmannia eruciformis so: kratkotrajne in nizke poplave spomladi, upad podtalnice v začetku poletje in razmeroma visok nivo talne vode v naslednjem delu vegetacijske dobe. Nasprotno pa se vrsta ne pojavlja na rastišču, če so vremenske razmere neugodne (sušna leta).