Pope Benedict XVI celebrates Christmas Eve Mass on Saturday night, kicking off a busy two weeks of public appearances that will test his stamina.
Hours before the evening Mass began, Benedict lit a candle in his studio window overlooking St. Peter's Square in a traditional sign of peace.
A few hundred people had gathered in the square to watch the candle lighting and the unveiling of the Vatican's larger-than-life nativity scene.
The Christmas Eve Mass was moved up to 10 p.m. from midnight several years ago to spare the pope a late night that is followed by an important Christmas Day speech.
In a new concession this year, the 84-year-old Benedict is expected to process down the basilica's central aisle on a moving platform to spare him the long walk.
On Sunday, Benedict will deliver his traditional "Urbi et Orbi" speech, Latin for "to the city and the world," from the central loggia of St. Peter's overlooking the piazza. Usually, the speech is a survey of sorts of the hardships and wars confronting the globe. He's also due to deliver Christmas greetings in dozens of languages.
Next weekend, he'll preside over a New Year's Eve vespers service, followed by a New Year's Day Mass.
A few days later he'll celebrate Epiphany Mass followed by his traditional baptizing of babies in the Vatican's frescoed Sistine Chapel.
Security was expected to be tight Saturday night as it has been in recent years.
In both 2008 and 2009 there were Christmas Eve security breaches, in which a woman with a history of psychiatric problems and wearing a telltale red sweat shirt jumped the wooden security barrier along the basilica's central aisle.
In 2008, the pope's security detail blocked her from getting to Benedict.
But in 2009, she managed to grab Benedict's vestments and pulled him to the ground.
The pope was unhurt and continued along with the service, but a French cardinal who was nearby fell and broke his hip.