John Boehner has survived a House rebellion by winning a third term as House speaker after Republicans took control of both chambers for the first time in eight years.
Twenty five Republicans voted against him.
At the top of the Republican agenda is approval of the Keystone XL pipeline, which was the first bill introduced.
Republicans won a majority in the Senate during November’s mid-term election.
They already controlled the House of Representatives.
They have been angered by recent unilateral actions by President Barack Obama including an executive action on immigration policy and a major shift in US policy on Cuba.
Both chambers convened at midday, as required by the US constitution, after an early morning storm that left the capital city covered in snow.
“Hard work awaits,” said the new Senate majority leader, Mitch McConnell.
“I’m really optimistic about what we can accomplish.”
During prepared remarks on January 6, John Boehner said he wanted Barack Obama to work with Republicans on bills that have stalled in recent years.
He also criticized unnamed fellow representatives for “shadow boxing and show business”.
The first bill to be introduced was the approval for Keystone XL, a controversial oil pipeline extension on hold for years.
It may have enough support to pass a procedural hurdle in the Senate but on Tuesday, the White House has said Barack Obama would veto the legislation if it came to his desk.
White House spokesman Josh Earnest said the legislation undermined a “well-established” review process and did not take into account a lawsuit still pending in the state of Nebraska over the pipeline’s route.
President Barack Obama has used his power of veto twice in his six years as president, but has said he expects to use it more now that both chambers are controlled by Republicans.
Republicans are also set to take on Barack Obama’s immigration policy changes through a funding fight, legislation to repeal or defund the health law often referred to as “ObamaCare”, and fast-track a Pacific trade deal.
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