Argentina's Congress has 257 members in the Chamber of Deputies (Cámara de Diputados) and 72 in the Senate (Cámara de Senadores)
Background
The Dirección Nacional Electoral records that the Congreso de la Nación (Congress of the Nation) is a bicameral assembly made up of the Cámara de Diputados (Chamber of Deputies) with 257 representantes and the Cámara de Senadores (Senate) with 72 representantes.
Freedom House's Argentina country report sets out the same composition in English: the National Congress consists of a lower house, the Chamber of Deputies, and an upper house, the Senate; the Chamber of Deputies has 257 members elected for four-year terms and the Senate has 72 members elected for six-year terms, and half of all deputies and a third of senators are up for election every two years.
Article 45 of the Constitution has deputies elected directly by the people of the provinces, of the city of Buenos Aires and of the Capital in case of transfer, which are treated for this purpose as electoral districts of a single State, by simple plurality of votes.
Article 50 gives deputies a term of four years and makes them re-eligible, but the chamber renews half of its seats every two years.
Article 54 composes the Senate of tres senadores por cada provincia and three for the city of Buenos Aires, elected directly and jointly, with two seats going to the party that wins the most votes and the remaining one to the party next in votes.
Article 56 gives senators a term of six years and allows indefinite re-election, while the Senate renews a third of its electoral districts every two years.
The Senate's own page states that the 1994 constitutional reform introduced the direct election of senators and a third senator for the minority in each district, and cut the senatorial term from nine years to six.
Article 57 makes the Vice-President of the Nation the president of the Senate, with no vote except to break a tie.
Article 52 reserves to the Chamber of Deputies alone the initiative on laws about contributions and the recruitment of troops.
In plain words
Bicameral Two-chamber legislature — A legislature with two separate houses, both of which must pass a bill before it becomes law.
Cámara de Diputados Chamber of Deputies — The lower house of Argentina's Congress, whose members represent the provinces and the capital city as electoral districts.