WASHINGTON (AP) October 3, 2005 — John Roberts, who argued more than three dozen cases before the Supreme Court as an appellate court lawyer, got to see a new side on Monday.

He took his seat -- a leather chair, actually -- as chief justice.

On opening day of the court's 2005-06 term, Roberts welcomed new lawyers to the Supreme Court bar and presided over arguments in two cases. He put on eyeglasses to read from the sheaf of papers in front of him, removed them to survey the packed courtroom and sipped from a silver cup.

Crisp and businesslike, Roberts, 50, listened intently, at times with chin in hand.

It was a younger and more robust version of his mentor, the late William H. Rehnquist, who died last month of cancer at age 80 after 33 years on the high court, including 19 as chief justice.

But unlike his predecessor, who had adorned each sleeve of his robe with a set of four gold stripes after being inspired by a costume in a comic opera, Roberts wore a plain black judicial robe.

Before taking his place in the chief justice's center chair, Roberts was welcomed during a special sitting of the nine-member Supreme Court. Bush, Attorney General Alberto Gonzales, Solicitor General Paul Clement, Senate Judiciary Committee Chairman Arlen Specter, R-Pa., and other senators, Roberts' wife, Jane, also a lawyer, and the Roberts' two children attended, among others.

Gonzales, wearing a formal morning coat with tails, brought Roberts' commission -- a poster-sized, ivory-colored document that Bush signed stating his intent to nominate Roberts to be chief justice. It was unrolled and read aloud before Justice John Paul Stevens, the most senior justice, administered the oath to Roberts in a repeat of his swearing-in at the White House last Thursday.

Stevens, 85, then wished his much younger boss ''a long and happy career in our common calling.''

After the brief ceremony, the pair -- in suits rather than their judicial robes -- posed for pictures on the Supreme Court steps before Roberts motioned for his waiting family to join him.

Four-year-old Jack, an active boy who manages to steal his father's limelight when they appear together in public, gazed at the long flight of steps before him as if he wanted to make a run for them.

His mother seemed to catch on and gripped his hand before letting him go to run, arms open wide, to Roberts, who scooped him up into a big hug. Roberts then hugged daughter Josie, 5, before exchanging a kiss with his wife and posing for news photographers.

''We love you Judge Roberts. We are praying for you and your family,'' shouted someone from the crowd that gathered in front of the court and had been singing until he appeared.

About an hour later, Roberts took his seat on the court. His full head of dark brown hair stood out in contrast to the gray heads on either side of him -- Stevens and the retiring Sandra Day O'Connor, 75.