The article describes the old-Polish institution of entailed estate, mostly exemplified by the 1589 Zamoyski entailed estate. Firstly, its legal regulation and practice of functioning is analysed within a broader perspective of the overall property and succession law in the times of their establishment. Then the functions, possibilities, but also challenges and problems connected with it are discussed. Finally, the utility of this study is presented for history, history of law, and modern law.