Currently, the Senate comprises 81 seats. Three Senators from each of the 26 states and three Senators from the Federal District are elected on a majority basis to serve eight-year terms. Elections are staggered so that two-thirds of the upper house is up for election at one time and the remaining one-third four years later.
The Federal Senate of Brazil was first established, with the name of Senate of the Empire, by the Constitution of 1824, the first enacted after the Declaration of Independence.
Following the independence, in 1822, Emperor Pedro I ordered the convocation of a National Assembly to compose the country's first Constitution. Following several disagreements with the elected deputies (which included representatives from present-day Uruguay, then part of the Brazilian Empire under the name of Província Cisplatina), the Emperor dissolved the Assembly and, in 1824, implemented the first Constitution, in which it was established that the Legislative branch would comprise a lower house, the Chamber of Deputies, and an upper house.
The first configuration of the Senate was a consulting body to the Emperor. Membership was for life and it was a place of great prestige, to which only a small part of the population could aspire.
Members of the Senate were elected, but they had to be at least 40 years old and, which was more significant as a limiting factor, an annual income of 800,000 contos-de-réis was necessary in order to run for office. Furthermore, voters were selected by income as well. In order to be able to vote in the election, any man (women did not vote in the Brazilian Empire) was required to have an annual income of at least 200,000 contos-de-réis. But those who qualified to vote with this income would not vote directly for the Senators; instead, they voted for other people, who were candidates to be Senator electors. In order to run for this position, a minimal annual income of 400,000 contos-de-réis was required. Once elected, these electors would vote for senator. The election itself would not turn out a winner automatically. The three highest-voted candidates in each circumscription would make up what was called a "triple list", from which the Emperor would select one individual that would be considered "elected". The Emperor usually picked the highest-voted individual, but it was within his discretion to select whichever of the three individuals listed. The only exception for these rules were the Princes of the Brazilian Imperial House, who were senators by right and would take a seat in the Senate upon reaching 25 years old.
The original Senate had 50 members, representing all of the Empire's Provinces, each with a number of senators proportional to its population.
The first session of the first Senate took place on May 1826, following repeated delays from the Emperor in calling the first election after the inception of the 1824 Constitution; which had led to repeated accusations that the Emperor would be attempting to establish an absolutist government.
^"Senado Federal completa hoje 185 anos". R7 (in portuguese). 6 May 2011. Retrieved 22 May 2012. "O Senado Federal foi criado com a primeira Constituição do Império, outorgada em 1824, inspirado, primeiramente, na Câmara dos Lordes da Grã-Bretanha. Sua primeira reunião ocorreu em 6 de maio de 1826."