Rehnquist, 80, one of the nation's most powerful and conservative jurists who has been on the court for more than 30 years, was admitted to Bethesda Naval Hospital on Friday and underwent a tracheotomy on Saturday, spokeswoman Kathy Arberg said.
She said in a statement that Rehnquist was expected to be on the bench when the high court reconvenes on Nov. 1 after a two-week recess. He is expected to be released from the hospital later this week, she said.
Supreme Court justices serve until they die or retire. The last change in the court's composition took place more than 10 years ago, the longest period of stability since 1823.
The current court is generally split by a 5-4 vote along conservative and liberal lines.
In the last U.S. presidential election, the Supreme Court by a 5-4 vote with Rehnquist in the majority halted a recount in the disputed Florida race, making President Bush the winner over Democrat Al Gore.
REHNQUIST: NO POLITICS IN BUSH V. GORE RULING
The day after the historic ruling, Rehnquist maintained that politics played no role in the court's decision-making.
As a justice for 15 years and then as chief justice since 1986, Rehnquist has led a conservative legal revolution to expand states' rights while limiting the federal government's power, to restrict appeals by death-row inmates and to allow more public funding of religious activities.
Arberg was unable to provide any details about the type of thyroid cancer that Rehnquist has, whether it has spread and his treatment.
Thyroid cancer is an easily cured form of cancer, with surgery and radioactive iodine working in most cases to clear it. Nearly all patients who have part or all of the thyroid removed must take thyroid hormone pills afterwards for life.
According to the American Cancer Society, various forms of thyroid cancer are expected to affect 23,600 Americans in 2004. It will kill an estimated 1,500 people this year.
Rehnquist was appointed to the court in 1972 by President Richard Nixon. He was elevated to chief justice in 1986 by President Ronald Reagan.
The Senate confirmed him by a vote of 65 to 33 but only after three months of stormy controversy over his record on civil rights and other issues. The number of dissenting votes was unusually high for a successful Supreme Court nominee.
If there is a Supreme Court vacancy, the president would nominate the replacement, who must be confirmed by the Senate.
Bush and his Democratic rival, Sen. John Kerry, have expressed differing views on the type of justices they would appoint.
Bush has cited Justices Antonin Scalia and Clarence Thomas, both staunch conservatives, as models for his appointments while Kerry has cited his vote in the Senate to confirm Scalia as one of his biggest regrets.
Over the years, Rehnquist has generally been in good health. He had surgery in 1995 for a back problem. Nearly two years ago, he underwent surgery to repair a torn tendon in his knee.