William H. Rehnquist, the 16th Chief Justice of the United States and a leader of the court's conservative bloc for three decades, died Saturday evening at his home in Arlington, a court spokesman announced.

Rehnquist, 80, has been undergoing treatment for thyroid cancer since October.

His death creates the first vacancy for a chief justice since 1986.

Court spokesman Kathy Arberg said Rehnquist was surrounded by his three children when he died, the Associated Press reported.

"The Chief Justice battled thyroid cancer since being diagnosed last October and continued to perform his dues on the court until a precipitous decline in his health the last couple of days," she said.

Rehnquist's death provides President Bush with yet another vacancy to fill on the court. He nominated John G. Roberts Jr. earlier this summer to succeed Justice Sandra Day O'Connor, who announced her retirement on July 1. Hearings on the Roberts nomination are scheduled to begin Tuesday.

The announcement follows months of speculation and rumor about Rehnquist's health. The frenzy prompted Rehnquist to put out a statement on July 14 saying he wanted "to put to rest the speculation and unfounded rumors of my imminent retirement. I am not about to announce my retirement," he said. "I will continue to perform my duties as chief justice as long as my health permits."

Bush now has a major opportunity to attempt to reshape the highest court in the land.

Rehnquist's death creates the need for two and perhaps three confirmation hearings. If Bush elevates a sitting justice to Rehnquist's position, confirmation hearings will be required for the designated Chief Justice, as well as for replacements for the associate justice elevated as well as for Roberts.

If he chooses a chief justice from outside the court, hearings will be required for that person and for Roberts.

Rehnquist was regarded as one of the most conservative justices in modern Supreme Court history, first as an often lone dissenter in the 1970s and 80s and later, when the court's makeup changed, as a stalwart of the conservative bloc.

He wrote and voted consistently in favor of expansive powers for police and prosecutors in criminal cases and in favor of the power of the states to impose capital punishment.

He believed the court had gone too far in separating church and state and voted to allow school prayer and public funding for many types of religious activity.

He dissented in Roe v. Wade, the 1973 decision legalizing abortion, and in all the cases upholding government sponsored affirmative action.

Scholars did not consider him a "strict constructionist," however, with a narrow view of the Supreme Court's powers. He was quite prepared to strike down acts of congress or of the federal government especially when they interfered with powers he considered reserved for the states.

Rehnquist was also universally considered one of the smartest members of the modern court, whose efficiency in putting out coherent opinions was legendary.

Rehnquist was appointed to the court by President Richard M. Nixon on October 21, 1971, to replace retiring Justice John Marshall Harlan. He was confirmed by a 68-26 Senate vote and sworn in on January 7, 1972. He had been an assistant attorney general in the Nixon administration's Justice Department.

In June 1986, President Ronald Reagan nominated Rehnquist to replace retiring Chief Justice Warren E. Burger. After a bitter partisan controversy -- centered in part around Rehnquist's views and political activities as a lawyer -- he was confirmed by a vote of 65-33 and sworn in on Sept. 26, 1986.

Rehnquist revealed his treatment for thyroid cancer on Oct. 22. After a five-month hiatus for intensive treatment, he returned to oral arguments at the Supreme Court in March, walking under his own power.

Once oral arguments got underway, he appeared as alert and informed as ever, peppering lawyers with questions and smiling at the occasional wisecracks of his colleagues during the two-hour sitting.