Only a few of the 115 cardinal electors taking part in the conclave starting on Tuesday are considered pontiff material, or "papabile". Here are some of the top contenders to become the next head of the world's 1.2 billion Catholics, as cardinals gather in the Sistine Chapel:
Angelo Scola:
The 71-year-old archbishop of Milan is a keen promoter of inter-religious dialogue, particularly between Muslims and Christians.
He is also an expert on bioethics, an issue on which Roman Catholic Church teachings are currently lagging behind scientific advances.
The son of a socialist truck driver, Scola is one of the closest heirs to Benedict XVI, combining conservative views with progressive social advocacy on issues like immigration and poverty.
He is Italian but is not associated with the Vatican bureaucracy, whose image has been badly tarnished by infighting in recent years.
Odilo Scherer:
The 63-year-old Brazilian is archbishop of Sao Paolo, home to five million faithful in a country that has the world's biggest Catholic population.
Scherer, whose family descended from German immigrants, is seen as a moderate conservative with charisma and openness, as well as a good administrator.
He has fought against declining traditional values and is concerned about the growing strength of evangelical churches across the developing world.
{{/usCountry}}He has fought against declining traditional values and is concerned about the growing strength of evangelical churches across the developing world.
{{/usCountry}}Scherer is well acquainted with social problems in Sao Paulo, a cosmopolitan city of 11 million people facing high poverty rates, crime, youth unemployment and lack of basic services.
On his archdiocesan website and in newspapers, Scherer regularly offers commentary on key issues. He is also very active on Twitter, boasting 20,000 followers of his account @DomOdiloScherer.