The National Congress (Congreso Nacional) consists of two houses, the Senate (Senado) and the Chamber of Deputies (Cámara de Diputados).

The Senate (Senado) has 38 seats elected by popular vote. Senate members serve eight-year terms, with one-half elected every four years. The current Senate contains 19 members from the center-left governing coalition (Concertación), 16 from the rightist coalition (Alianza por Chile) and 3 Independents.

The regions with the largest populations - Metropolitan Region and Regions V,VII, VIII, IX and X - have 4 Senators each, while each of the other regions is represented by two Senators.

The Chamber of Deputies has 120 seats. Members are elected by popular vote to serve four-year terms. The current lower house contains 59 members from the Concertación, 52 from the Alianza por Chile, and 9 independent members.

Each of sixty districts in the country is represented by 2 Deputies. The Congress is located in the port city of Valparaíso, about 140 kilometers (84 mi.) west of the capital, Santiago.

The bi-nominal electoral system used for congressional elections makes it hard for small parties to win seats unless they are part of a substantial coalition. It also makes it difficult for a coalition to win a large congressional majority, encouraging consensus solutions and political co-operation between the government and the opposition.

Depending on the type of law proposed, bills require different types of majorities to be approved (simple majority, 2/3 or other). Bills may be introduced in the Chamber of Deputies or Senate. When they are first approved by the Chamber of Deputies, they then must be approved by the Senate to become a law.