Sonia Sotomayor was sworn in Saturday morning as the first Hispanic justice on the Supreme Court in a brief ceremony that completed a remarkable ascent for a Puerto Rican girl from the South Bronx.

Sotomayor, 55, rested her left hand on a Bible held by her mother and raised her right hand as Chief Justice John G. Roberts Jr. administered a pair of oaths that made her the 111th justice to serve on the nation's highest court. She pledged to "administer justice without respect to persons and do equal right to the poor and to the rich."

The chief justice had slightly flubbed the wording of the oath of office when he swore in President Obama in January; this time he held a piece of paper containing the oath for Sotomayor. Occasionally Roberts looked down as he recited the words.

Immediately after she repeated Roberts's words in a firm voice, the new justice, wearing a cream-colored suit and a wide smile, gave a long hug to her mother, Celina Sotomayor, and one to her brother, Juan, who stood at her side.

"Congratulations and welcome to the court," Roberts said.

The two-part ceremony began with a constitutional oath, dating to the 1860s, that Roberts administered privately in the justices' conference room near the rear of the Supreme Court building on Capitol Hill. They then walked to the court's paneled East Conference Room, where Sotomayor took the judicial oath before about 60 relatives and friends, standing beneath a portrait of John Marshall, the renowned 19th-century chief justice. The court permitted the second oath to be broadcast on television, marking the first live coverage of such a ceremony in the institution's history.

Besides Roberts, Justice Anthony M. Kennedy attended the ceremony, as did two members of the White House counsel's office who had helped select Sotomayor and shepherd her through the confirmation process. Friends whom Sotomayor invited included Robert Katzmann, with whom she served on the U.S. Court of Appeals for the 2nd Circuit, and Rep. Nydia Velasquez (D-N.Y.). The new justice attended a reception after the ceremony.

Sotomayor becomes the third woman to serve on the Supreme Court and the first appointee by a Democratic president in 15 years. Obama nominated her to replace David H. Souter, who announced in early May that, after 19 years as a justice, he intended to retire to his native New Hampshire.

Sotomayor became a member of the court two days after she was confirmed by the Senate on a 68 to 31 vote. She won the support of every Democratic senator except  Edward M. Kennedy (Mass.), who was too ill to be present, but fewer than one-fourth of the Republicans.

Her swearing-in took place on a Saturday to accommodate relatives and friends attending from out of town.

During the 10 weeks between Sotomayor's nomination and the Senate vote confirming her, Obama, Democratic senators and their allies portrayed her as a seasoned and moderate jurist with 17 years on the federal bench, as a trial judge in Manhattan and then as an appellate court judge.

They also emphasized her biography. She was raised by a widowed mother in a South Bronx housing project. She went on to the Ivy League for college and law school, then worked as a prosecutor and at a private law firm with an international clientele before becoming a federal judge at age 38.

During the confirmation debate, Republicans criticized her on two grounds: statements she had made from the bench that they contended reflect ethnic and gender biases, and three cases on which she ruled that involved issues of discrimination and gun and private-property rights. 

On the eve of her swearing-in, White House officials said, Sotomayor had dinner with colleagues on the 2nd Circuit in New York, where she has been a judge for the past 11 years, before traveling to Washington.

Sotomayor has never lived south of New Jersey. According to people who know her, she plans to stay with friends in Washington until she decides where to reside.

Friends also said that, in the weeks since her confirmation hearings ended last month, Sotomayor, known for prodigious working hours, has begun reading to prepare for the first cases she will help to decide.

She will take her seat on the court in early September when the justices, in a rare act, will convene outside the court's normal schedule to consider a significant campaign finance case. She will begin her first full term on Oct. 5, the first Monday in October being the traditional start of the court's year.

After she was sworn in, Sotomayor went to a barbecue with her family and friends in Annandale, according to Dawn Cardi, a close friend who came from New York for the ceremony.

Before they left the court, Cardi said, friends were given a tour of the building. When they reached Sotomayor's chambers, a brass plaque with her name was already on the door. The new justice was seated to greet them at her desk.