WASHINGTON -- Chief Justice William H. Rehnquist was hospitalized last weekend after being diagnosed with thyroid cancer, the U.S. Supreme Court announced yesterday in a terse statement that said Rehnquist would be back on the bench for oral arguments on Monday.

The statement said Rehnquist underwent a tracheotomy on Saturday at Bethesda Naval Hospital "in connection with a diagnosis of thyroid cancer." The statement did not specify the type of thyroid cancer, and a court spokeswoman could not say whether Rehnquist would be able to ask questions at Monday's arguments.

Dr. John Yim, an assistant professor of surgery at the University of Pittsburgh and an expert on thyroid cancer, said that a tracheotomy -- an incision in the windpipe designed to ease breathing -- was not a usual procedure in early treatment of the most common kinds of thyroid cancer.

Dr. Yosef Krespi, chairman of otolaryngology at St. Luke's-Roosevelt Hospital in New York, told The Associated Press only aggressive or complicated thyroid cancers require a tracheotomy. Other physicians, however, said the procedure is sometimes done as part of routine thyroid surgery.

Rehnquist's age -- he turned 80 on Oct. 1 -- and the lack of details about the severity of his condition intensified election-year speculation about whom a re-elected President Bush or a newly elected President John F. Kerry might nominate to succeed Rehnquist, a pillar of the court's conservative wing.

Rehnquist, a former assistant U.S. attorney general with impressive academic credentials, was nominated to the court in 1971 by Richard Nixon and elevated to chief justice in 1986 by Ronald Reagan after stormy Senate confirmation hearings. A lonely dissenter in his early days on the court, Rehnquist later presided over a conservative majority that reversed or modified liberal precedents on issues ranging from aid to students in religious schools to criminal procedure and the allocation of powers between the states and the federal government.

Rehnquist sometimes has parted company with even more conservative justices who followed him on to the bench in the Reagan and George H.W. Bush administrations.

For example, in 1988 over a stinging dissent from Justice Antonin Scalia, Rehnquist wrote the majority opinion upholding a federal law providing for court-appointed independent counsels to investigate accusations against high-ranking federal officials. In 2000, Rehnquist spoke for the court in a decision reaffirming the court's 1966 ruling in Miranda vs. Arizona, which held that police must advise arrested persons of their rights before questioning them. Scalia and Justice Clarence Thomas dissented.

But on other issues, Rehnquist as chief justice has hewn to the conservatism of his early years. He was one of two dissenters in the 1973 case of Roe vs. Wade in which the court ruled that a constitutional right of privacy was broad enough to encompass a woman's right to choose abortion.

In the 1992 Pennsylvania case in which the court reaffirmed the "essential holding" of Roe, Rehnquist dissented.

Except for a chronic back condition, Rehnquist, a widower, has shown no signs of ill health and, along with 84-year-old Associate Justice John Paul Stevens, has been active in questioning lawyers during the 2004-2005 court term that began on Oct. 4.

The conventional wisdom among court-watchers has been that both men -- and possibly 74-year-old Justice Sandra Day O'Connor -- are likely to leave the court during the administration of the president elected this year.

Only one member of the court -- Thomas -- is under the age of 65.

In the third televised presidential debate Kerry promised that he would not choose anyone for the court who would vote to make abortion illegal again. Bush, while on record as praising Scalia and Thomas, said in the debate that he would not apply a "litmus test" in choosing justices.