The goal of this thesis is to show the life and functioning of the Senate of the National Assembly of Czechoslovakia. The upper house of the Czechoslovak Parliament functioned between 1920 and 1939 after which it was officially dissolved during the Protectorate of Bohemia and Moravia. In the concerned period, the chamber was gradually saw 444 lawmakers of seven different nationalities. The biggest number consisted of Czechs and Germans. The functioning of the Senate is analyzed from multiple angles. First the debate accompanying the establishment of a second chamber before the adoption of the new Constitution in 1920 is analyzed. Attention is also paid to the period debates and unrealized proposals for a Senate reform at the end the 1920's, linked to the proposed creation of the Economic Parliament. Also shown is the proportional representation electoral system used for elections to the Senate. The results were reflected in a large number of political parties with low electoral gains, which in turn hindered the creation of a stable political environment. The thesis considers the party, ethnic, social, intellectual and oratory activities of individual senators. The lives of some of the lawmakers who held seats in the upper chamber in the First Republic and were negatively affected by the German...