US President George W Bush handed power to Vice-President Dick Cheney for just over two hours while he underwent a routine check for cancer of the colon.
President Bush underwent a similar health check in 2002
Five small growths, or polyps, were removed during the colonoscopy but "none appeared worrisome", White House spokesman Scott Stanzel said.
Under the US constitution, power can be transferred to the vice-president if the president is incapacitated.
Mr Bush first had the minor procedure in June 2002.
It was performed on Saturday at the Camp David presidential retreat in Maryland.
Mr Bush was "in good humour" afterwards and ready to resume "his normal activities" at Camp David, Mr Stanzel said.
Mr Bush transferred his authority at 0716 (1116 GMT) to Mr Cheney and reclaimed it at 0921 (1321 GMT), the White House said.
The colonoscopy itself lasted 31 minutes.
The polyps were being sent off for routine microscopic examination with the results expected in between 48 and 72 hours.
The results would determine the final diagnosis and recommendations for future treatment, Mr Stanzel added.
During the transfer. Mr Cheney was at his home on Chesapeake Bay in Maryland, about 30 miles (50 km) east of Washington, the White House said.
It was authorised under Section 3 of the 25th Amendment to the US Constitution.
Earlier, presidential spokesman Tony Snow said Mr Bush had shown no symptoms of illness but was following doctor's advice to have a follow-up after the 2002 check.
The Associated Press news agency notes that Americans are advised to undergo a colonoscopy every 10 years but where polyps are found, follow-up checks are recommended at intervals of three to five years.