Those in the running to succeed Pope John Paul II are known as the papabili- those worthy of becoming Pontiff.
Prominent among them are:
Cardinal Joseph Ratzinger
A 77-year-old German who is known as John Paul II's ideological "enforcer". The slight, bespectacled, white-haired cardinal had been regarded as too old to become Pope but has recently been touted to succeed, perhaps in a transitional role. Cardinal Ratzinger has been in the Vatican for more than two decades and became one of John Paul II's closest collaborators.
John Paul II appointed him Prefect for the Congregation for the Doctrine of the Faith (CDF) - an organisation once known as the Inquisition - which has allowed him to stamp his theological conservatism on the Church over a period of more than 20 years.
His role and hard-line views saw opponents nickname him the "Panzerkardinal" but he also has many supporters and is the ultimate Vatican insider. In the corridors of the Vatican his other nicknames include "vice pope" and "John Paul III".
Cardinal Ratzinger has seen his mission as defending Catholic teaching following liberal moves after the Second Vatican Council in the 1960s. He has criticised the introduction of the non-Latin Mass as a "tragic breach". In the 1980s he described homosexuality as an "intrinsic moral evil" and said rock music could be a "vehicle of anti-religion".
To some he is a saviour to the Church in an increasingly secular world, to others he is an authoritarian who punishes liberal thought. He is undeniably an intellectual heavyweight who is fluent in four languages.
Cardinal Dionigi Tettamanzi, Archbishop of Milan
The 71-year-old is the likeliest Italian candidate and currently heads Europe's largest diocese with 4.8 million Catholics.
He is a highly respected theologian who specialises in sexual morality and bioethics. Doctrinally, Cardinal Tettamanzi is considered highly orthodox and is said to have taken care to align himself with Opus Dei.
But he is also known for his social commitment and a more populist position on globalisation. At the time of the anti-globalisation protests during the G-8 Summit in Genoa in July 2001, he said that "a single African child sick with Aids counts more than the entire universe".
He was once memorably described by a Scottish Archbishop as "that wee fat guy" and may also welcome a change of name as Pontiff. His name means "bullock breast".
Counting against Cardinal Tettamanzi is a relative lack of international experience. Being Italian may also for once not help. The election of the Polish Pope John Paul II broke the Italian stranglehold on the papacy and the conclave may seek a Pope from a new area of the world.
Tettamanzi endeared himself to much of the Italian public in 2003 when he was taken on a two-lap spin around the Monza Formula One motor racing circuit and visited the Ferrari pits ahead of the Italian Grand Prix. He took the opportunity to tell the sport to pay more attention to the poor.
Cardinal Claudio Hummes
A Franciscan and Archbishop of Sao Paulo, Brazil. The 70-year-old is a doctrinal conservative who supports decentralisation by increasing the powers of national conferences of bishops. The growing strength of the Catholic Church outside Europe and North America could also help his cause.
Cardinal Francis Arinze
A 72-year-old Nigerian who could become the first black man in 1,500 years to sit on the throne of St Peter. He is from humble beginnings in the Nigerian countryside where his parents worshipped traditional African gods.
But they sent him to an Irish missionary school as a child. He went on to join the priesthood, studied in London and became Africa's youngest bishop at the age of 32.
His current post puts him at number four in the Vatican hierarchy. Cardinal Arinze is seen as a conservative within the church, who takes a hard line on women priests, abortion and homosexuality. But he believes Muslims, Buddhists and Jews can go to heaven and has forged links with leaders of other faiths. He is regarded as personable, charming and a good communicator.