Clinton, 63, was transported to Columbia Presbyterian Hospital in Manhattan for a condition related to his heart.
ABC News' chief political correspondent George Stephanopoulos reported that sources said he was taken to the hospital "likely for a stent procedure."
Sources on Capitol Hill tell ABC News that Secretary of State Hillary Clinton was seen leaving the Oval Office a short time ago and did not seem "too concerned" or "in a rush."
State Department spokesman P.J. Crowley said Sec. Clinton is supposed to leave for an overseas trip to Qatar and Saudi Arabia Friday.
An official told ABC News that Clinton's ailment seems more like "discomfort…something wasn't right" rather than a health "crisis."
A friend of the former president's said that he had been suffering from a cold and had been warn out from his recent trip to Haiti.
Clinton underwent quadruple bypass surgery at the same hospital where he is now a patient four and a half years ago.
ETA: CNN's John King reporting hospitalization due to chest pains.
Clinon's office has confirmed two stents in coronary arteries. - source: TV
"Today President Bill Clinton was admitted to the Columbia Campus of New York Presbyterian Hospital after feeling discomfort in his chest," said Douglas Band, counselor to the former president, in a written statement.
"Following a visit to his cardiologist, he underwent a procedure to place two stents in one of his coronary arteries. President Clinton is in good spirits, and will continue to focus on the work of his Foundation and Haiti's relief and long-term recovery efforts. In 2004, President Clinton underwent a successful quadruple bypass operation to free four blocked arteries." (source)