Pope Benedict XVI reached out to believers of other religions during his installation ceremony in Saint Peter's Square.
Dignitaries from around the world joined hundreds-of-thousands of cheering people waving flags in Saint Peter's Square. Many watched the event on large video screens.
Special security measures included deploying 10,000 officers and closing Rome airspace.
The installation ceremony began with a procession by the pope and the cardinals to the grottoes underneath St. Peter's Basilica to pay homage at the tomb of Saint Peter. Then, they walked into the square to begin the public open-air mass.
The Ceremony of Investiture was celebrated by the senior cardinal deacon, Jorge Medina Estevez. The Chilean cardinal announced the new pope's name to the world after his election last Tuesday.
During Sunday's ceremony, Pope Benedict received his Fisherman's Ring and the Pallium, a woolen shawl with three red crosses. These are the symbols of the pope's pastoral authority.
Pope Benedict then spoke in Italian.
He said, "at this moment, weak servant of God that I am, I must assume this enormous task, which truly exceeds all human capacity." And he added with conviction that he knows he is not alone.
Pope Benedict then reached out to believers and non-believers. With great affection, first he greeted those not yet in full communion with Roman Catholics, but who have received the sacrament of Baptism.
And then he said, "and you, you, my brothers and sisters of the Jewish people, to whom we are joined by a great shared spiritual heritage."
Applause broke out when the pope said he did not need to present a program of governance. He said his real program would be not to do his own will, not to pursue his ideas, but to listen with the whole Church to the word and will of the Lord.
The pope's thought also turned to young people. He told them not to be afraid of Christ, because "he takes nothing away and gives everything." The pope said, "Open wide the doors of Christ, you will find new life."
At the end of the mass, Pope Benedict rode aboard an open-topped white jeep to greet the faithful. The pontiff smiled and repeatedly blessed the crowd as he was driven around the square.