(CNN) - Sen. Frank Lautenberg, D-New Jersey, was hospitalized Monday after taking a fall, his spokesman said.
The 86-year-old Lautenberg, who is in his fifth term in the Senate, was taken to the hospital as a "precautionary measure," spokesman Caley Gray said.
"The senator is in great spirits and joking with the doctors," Gray said.
He will remain at the hospital overnight for observation, Gray said.
UPDATE: Communications Director Caley Gray says Lautenberg was diagnosed with a bleeding ulcer Tuesday morning and "underwent a successful endoscopy procedure to treat it."
"After becoming lightheaded and taking a fall as a result of the condition, the Senator sought medical attention last night. The Senator is expected to make a full recovery and will be back to work soon," said Gray.
–CNN's Deborah Doft and Evan Glass contributed to this report.