From The Hill:

Senator-Elect Scott Brown, the successor to the late-Sen. Ted Kennedy, will be sworn in to office Thursday afternoon, giving Republicans 41 seats in the upper chamber.
“Once we get his certificate we expect to swear him in tomorrow afternoon as early as five o’clock, which is earlier than he suggested,” said Jim Manley, spokesman for Senate Majority Leader Harry Reid (D-Nev.), in an interview Wednesday.