Chief Justice William H. Rehnquist (search) was hospitalized briefly with a fever on Thursday, the second emergency treatment for the 80-year-old ailing justice in two months.

Rehnquist was treated and released from Virginia Hospital Center in Arlington, Va., the same hospital where he spent two nights for observation and tests in July, also after running a fever.

The chief justice has thyroid cancer, and his latest health problems will almost certainly renew questions about whether he is well enough to remain on the court.

The Supreme Court is already losing one member, Justice Sandra Day O'Connor (search), who announced her retirement on July 1. A second vacancy could complicate the confirmation of John Roberts (search), the appeals court judge named to replace her.

Rehnquist, who has been on the Supreme Court 33 years, has refused to disclose specific details about his illness but in July issued a statement pledging to remain on the job.

"I want to put to rest the speculation and unfounded rumors of my imminent retirement," he said July 14. "I will continue to perform my duties as chief justice as long as my health permits."

Edward Lazarus, a former Supreme Court clerk who practices law in Los Angeles, said people will now question the fragility of his health.

"Inevitably, two hospitalizations in a very short period of time is going to get people talking again about the chief justice retiring, and cast into a new light the Roberts' confirmation," he said.

Rehnquist had been working at the court earlier in the day Thursday and has maintained a full-time schedule. He was back at his home Thursday evening.

Supreme Court spokesman Ed Turner said: "The chief justice developed a fever today. He was taken to Virginia Hospital Center for evaluation. He was not admitted."

White House spokesman Scott McClellan, with President Bush at the president's ranch in Crawford, Texas, said: "We hope the chief justice is feeling better soon."

Rehnquist was diagnosed with cancer in October, and medical experts have said it is not uncommon for people with the disease to have fever, possibly caused by infection, pneumonia, allergies to medicine or reaction to chemotherapy.

When the Supreme Court (search) ended its term in late June, court watchers thought Rehnquist would be stepping down. Instead, O'Connor announced she was leaving and giving the court its first vacancy in 11 years. Bush chose as her successor Roberts, who once served as a law clerk to Rehnquist.