ENThe incorporation of the Duchy of Masovia into the Kingdom of Poland in 1526 (after the death of Janusz III, the last male member of the House of Piast of Masovia) and visits of Sigismund I and his court in Warsaw resulted in significant growth of the city. The king confirmed the old privileges and granted the new ones for Old and New Warsaw. The Old City was given a privilege restricting the trade of the visiting merchants, enabled the burgesses to produce and sell drinks and regulated the relationships between the patriciate and the common people, and finally, established three two-week fairs - for Mercy Sunday, and for days of St Anthony (13.06) and St Hedwig (15.10). Sigismund I cared about the development of craft in Old and New Warsaw. The monarch approved the existing guilds and freed them from the jurisdiction of the Krakow’s guilds. These were the privileges important for the craft, since each of the Warsaw guilds, after being exempted from the dependence on Krakow’s corporations in 1527 and granting them the judicial competences in 1531, became to a certain extent an independent professional institution. New Warsaw was granted a privilege in 1538 by the king that allowed her to establish scales in the Town Hall and build baths, from which the income was to be allocated for the needs of the town.Taking into consideration the complaint of the Warsaw burgesses about the Jews living in the city, the king gave a privilege De non tolerandis Judaeis in 1527, in which he forbade the Jews to live in Old and New Warsaw as well as in the suburbs. Since the incorporation of Masovia into the Kingdom, the Polish king, who showed considerable interest in hospitals located in Old and New Warsaw, exercised supervision over them. In the travels of Sigismund I we can observe a future “sejm” role of Warsaw as a link between the Kingdom and Warsaw, which may testify to the advancement of Warsaw as a convenient place on the more important “sejm” route of the Jagiellons - from Lithuania to Piotrków.