ENThis publication has been devoted to the institute of Seym (the Lower House or Parliament) as the most import organ of the noble democracy at the turn of 16th and 17th centuries (1587-1632). Its operations was regulated by three most important acts: the Nihil novi constitution of 1505, the union and resolutions of the Lublin seym of 1569 as well as King Henry s Articles of 1573. In addition, until the time of the coronation of the prince of Sweden, Sigismund Waza, as the king of the two nations, other constitutions of less significance, as well as the seym customs used for many years also constituted the basic operations of the seym. In all the previous literature dominated absolutely the argument that King Henry s Articles provided for the division of the seym into ordinary (lasting - six weeks) and extraordinary (lasting - two or three weeks). The latter, as is stated to this day, were to be summoned by the king as a result of sudden needs of the state, with the consent of the senators. Detailed research carried out by the author has confirmed the fallacy of this argument. This is because King Henry s Articles provided for one type of seym. This was an ordinary seym summoned for a period of up to six weeks, every two years or more frequently, when the situation of the state demanded thus. However, this seym was always summoned according to the same principles, with the consideration of all the necessary seym operations. Not long after, that at the start of the reign of Sigismund III (1591), the seym, by way of passed constitution, carried out the interpretation of the period in which the seym was to last, amending thus the then regulations of King Henry’s Articles. From hence forth the seym was to last exactly six weeks, counting from the time of its summon, determined and an-nounced in the king’s proclamations.Its closing after the end of six weeks, on a day corresponding to the day of its start (from henceforward it was not to be a Sunday or any church holiday), meant that the seym was to last exactly 43 days. The seyms known as extraordinary appeared as a result of a need to summon unplanned and unusually complicated state difficulties. For the first time it was planned to summon such a seym (two weeks, with partial resignation of some of the activities of the seym) in 1595 in the face of imminent danger of a war with the Turkey. However, the call for seym session did materialize because the situation on the southern border became calm. However, the constitution of the Krakow seym, providing for procedure of summoning extraordinary seym was to be used in later times, because as a result of Dymitriads a plague of demands fell on the Republic from the soldiers - confederates, who had started to devastate the whole stretches of the country, demanding payment of exorbitant, beyond all measures, soldier’s pay. The situation of the state, from week to week, was becoming more and more tragic. The treasury was empty; there was not time for protracted actions aimed at summoning an ordinary seym. The king decided to call a short, two-week seym, giving reasons for his action as the requests from the nobles themselves, who were being constrained by the confederates. The noble circles widely proclaimed the seym as illegal. The accusation would have been misplaced, if the legal basis of summoning it had been King Henry s Articles. Eventually the seym was summoned on the autumn of 1613, it was concluded with the passing of huge taxes for the settlement of the payments for the army.Since then, with time, extraordinary seyms were summoned more and more frequently with the legal force of previously passed seym resolution, which had the king’s authorization in this issue. It was therefore lex specialis, which passed the general law - King Henry s Articles. The nobility regarded these seyms as inconsistent with the legal regulations and non-stop demanded a stop to their call. However, in practice they still function due to the need to undertake quick actions under very difficult circumstances that affected the Republic in the second and third decade of the 17th century. In accordance with concept of seym the state shaped in the period of the first interregnum as well as with reference to the Nihil novi constitution it was accepted that general seym were to continue to be summoned even after entering into union with Lithuania - royal, it comprised of three seym states: king, senate as well as parliamentary chamber. During the reign of Sigismund III the status of the Member of Parliament was the most often subjected to legal regulations. A nobleman convicted of infamy or banished as well as one sued by the seym court was prohibited to hold the office of Member of Parliament. In addition, members of the tribunal as well as tax collectors who had not settled up the accounts for the collected money were also included in the probation from assuming this function. In those days, as a rule, a member of parliament would be, at least, 23 of age, and speak Polish and Latin, this created some difficulties for the Lithuanians. Each of the seym states had its authorizations and responsibilities in the seym. The rising role of the parliament chamber, which precisely assumed the helm of the seym issues, can then be seen, although in order to pass a resolution the approval of all the three seym states was still necessary. [...].