The Senate has 36 seats. Each of the country's nine departments returns four senators elected by proportional representation (D'Hondt) (Until 2009 the Senate had 27 seats: three seats per department: two from the party or formula that receives the most votes, with the third senator representing the second-placed party.) Senators are elected from party lists to serve five-year terms, and the minimum age to hold a Senate seat is 35 years.
The Chamber of Deputies comprises 130 seats: 77 deputies are elected to represent single-member electoral districts, and an additional 53 are elected by proportional representation from party lists on a departmental basis. Deputies also serve five-year terms, and must be aged at least 25 on the day of the election. For the 2005 general election, seats were reapportioned, making 70 single-member electoral districts (60 are elected by proportional representation).