The 80-year-old Rehnquist has not been on the bench since October, when he disclosed the illness, but reads transcripts of the arguments and participates in decisions.
He was among the four-justice minority in Tuesday's landmark ruling outlawing executions of killers who were juveniles when they committed their crime. And he authored Wednesday's unanimous decision finding former foreign spies can't sue the government over claims they were promised more than they got for their clandestine work for the United States.
The court next hears arguments on March 21. It's unclear whether Rehnquist will return to the bench then. The court generally has waited until the Friday before the next round of arguments to announce whether Rehnquist will attend.