Pakistani lawmakers are voting for new senators in an election that could increase Prime Minister Nawaz Sharif's ability to pass laws.
Members of four provincial assemblies and the lower house of the federal parliament are choosing from among 132 candidates for 48 seats in the upper chamber.
Results are expected later on March 5.
The main opposition party, the Pakistan People's Party, currently holds a majority in the Senate.
But after the March 5 vote, Sharif's ruling Pakistan Muslim League, which holds a majority in the lower house of parliament, is expected to win almost equal representation in the upper house.
Under the constitution, a bill must be passed by both chambers and then ratified by the president to become law.
Sharif became prime minister for a third time in 2013.
He is facing a number of pressing issues, including a Taliban insurgency, an embattled economy, and chronic power shortages.