ASHINGTON, Nov. 26 - Chief Justice William H. Rehnquist, who missed the Supreme Court's November argument session while being treated for thyroid cancer, will be absent for the December session as well, the court announced on Friday.

Kathleen Arberg, the court's public information officer, said Chief Justice Rehnquist was continuing to receive chemotherapy and radiation treatments as an outpatient and was meeting with his law clerks and court officials at his home. Ms. Arberg said she had no information on when the 80-year-old chief justice might return to the court.

Given the apparent seriousness of his illness, there has been widespread speculation that the chief justice will announce his retirement sometime this winter. Jan. 7 will mark his 33rd anniversary on the court.

The court hears arguments in 12 cases over a two-week period during most months of its term. The two-week session that begins on Monday will be the last of the year.

Justice John Paul Stevens, who is presiding over the arguments in the chief justice's absence, announced at the beginning of each day of arguments during the November session that Chief Justice Rehnquist would participate in the decisions by reading the briefs and argument transcripts in each case. During the chief justice's monthlong absence from the court, he has taken part from home in the court's decisions on which new cases to accept for review.

Whenever a justice does not participate, for any reason, in the consideration of a case, that fact is noted on the court's weekly list of orders, and there has been no indication with respect to Chief Justice Rehnquist. Presumably he plans to take part in the cases on the December calendar as well.