The former Iraqi vice-president known as "Saddam's knuckles" has been captured by Kurdish fighters in Iraq.
Ramadan was known as an enforcer
Taha Yassin Ramadan was seized in the northern city of Mosul on Monday and has now been handed over to the US Army.
Mr Ramadan had been on America's "most wanted" list of Iraqi officials and is accused of a role in the repression of Iraqi Kurds as well as Shia Muslims.
US President George W Bush welcomed the news of the capture, Reuters news agency reports.
"I'm really pleased that we've captured the vice president. Slowly but surely we'll find who we need to find," he told reporters at his ranch in Texas.
TAHA YASSIN RAMADAN
Born near Mosul in 1938
Started career as bank clerk
Joined Baath party in 1956
Headed court which put to death "plotters" against the new regime after 1968 coup
Became vice-president in 1991
The BBC's Susannah Price says the capture could provide the coalition with new information about the ousted regime and Saddam Hussein himself, who is believed by some to have survived the war.
"He was detained in Mosul as a result of co-operation between
the political parties and residents," Adel Murad, a spokesman for the Patriotic Union of Kurdistan (PUK), told Reuters news agency in Baghdad.
Diane Perry, a spokeswoman for the Pentagon, confirmed that Mr Ramadan had been turned over to the US Army on Tuesday.
According to unconfirmed reports, Mr Ramadan was dressed as a peasant at the time of his capture, and had been living among relatives or friends.
The former vice-president figures as Number 20, or the 10 of Diamonds, in the "most-wanted" pack of cards issued by the US after this year's invasion of Iraq.
He is suspected of involvement in some of the most lethal operations conducted by Saddam's regime:
the occupation of Kuwait which led to the first Gulf War in 1991
- the repression of the Shia Muslim uprising of the same year
- the killing of thousands of Kurds in the town of Halabja in 1988 by poison gas
He is also said to have presided over political purges aimed at strengthening Saddam's control.
Now in his sixties, Mr Ramadan is originally from the region around Mosul, which has a mixed population of Arabs and Kurds.
Saddam's eldest two sons were killed in a house siege in the city in July after being betrayed to US troops.
'Harder than Saddam'
Mr Ramadan had a reputation for rhetoric even more anti-American than that of Saddam, once describing the US Congress as an extension of Israel's Knesset, or parliament.
His devotion to the leader appears to have been total and stretches back to the early days of the Baath party's rule.
On a visit to Jordan in the 1980s, he was asked by Islamic fundamentalists what the regime ruling mainly Muslim Iraq thought of Islam.
Muslims were free to follow their faith, he said, but: "If they try to harm the Baathist regime or ridicule its slogans, the regime will
break their necks!"