Introduction:
The paper presents the results of floristic research carried out in the Psarski Stream Valley in Będzin. The local flora was described with special attention to regionally rare, endangered, protected, and medicinal plant species.

Material and methods:
The field research was carried out in the vegetation seasons in 2011–2012 using the standard floristic investigation method, and the floristic list was made. Besides the names of all the plant species, the list includes information about endangered species and their legal protection. The possibilities of using the plants in folk medicine as well as in official therapy in Poland (plants described in Polish Pharmacopeias No. 10) were also indicated.

Results:
The total number of vascular plant species in the studied area in 2011–2012 is 295 and the results of the field research were compared with literature data. We failed to confirm 14 further species which were reported from this area in 2 earlier publications. There are 106 species of medicinal plants (36%) and 37 of them are described in Polish Pharmacopeias No. 9. Eight species of the studied flora are legally protected and 20 species belong to rare and endangered plants in the Silesian province. The most interesting new floristic find for this area is siberian iris (Iris sibirica L.), which was earlier incorrectly considered extinct in the studied region.

Conclusions:
Because of the rich biodiversity of the studied stream valley, this area plays an important role of a major refuge for many rare and endangered plants of the region. Due to the large number of plant species occurring in the studied area, those plants could be used as a natural seed bank especially the rare and protected plants, and also for many scientific purposes.