Cardinal Peter Erdo, 60, of Budapest, Hungary, is a local bishop with international experience.
Pope Benedict has assigned him to various tasks in the developing world and he currently serves as president of the Council of European Bishops' Conferences, a sign that his fellow bishops view him with great respect.
A canon lawyer, Erdo has spoken with authority on a wide range of topics and seeks to foster dialogue between faith and science.
He is also considered a good pastor who has worked hard to revitalize the Church in his diocese and across Hungary.
Although not well known in North America, he could be a serious contender.
Cardinal Timothy Dolan, 63, of New York may have the greatest personal popularity of any of the men with red hats.
The former rector of the North American College, the U.S. seminary in Rome, is gregarious and self-effacing.
He has also been archbishop of Milwaukee after serving briefly as auxiliary bishop in his native St. Louis.
In Milwaukee, a sexual abuse scandal became public early in his term, but he nevertheless managed to increase the number of men entering the seminary.
Time magazine has named Dolan one of the most 100 influential people in the world and he is currently the president of the U.S. bishops' conference.
Cardinal Christoph Schonborn, 68, has been on the hot seat since becoming archbishop of Vienna in 1995. He has had to deal with dissenting priests, the sexual abuse issue and massive parish closures in his diocese.
Through it all, Schonborn, a member of the Dominican order, has become known as a man of dialogue who prefers a patient approach to harsh clampdowns. The solution to problems in the Church, he says, is a rediscovery of the faith.
He earned his doctorate studying under Joseph Ratzinger and was also the main editor of the Catechism of the Catholic Church.
Considered papabile in 2005, he may be ever more so this time.
Cardinal Robert Sarah, 67, served 21 years as archbishop of Conakry, Guinea, and courageously defended human rights against a Marxist government that ruled for five of those years.
Since 2010, he has been president of Cor Unum, the Vatican agency for charitable giving. Prior to that, he was secretary for nine years of the Congregation for the Evangelization of Peoples. Both jobs required extensive travel and Sarah is well known in the developing world.
He became a bishop at age 34, making him the youngest bishop in the world at that time.
Sarah has said Africa must defend itself from the "contamination" of Western ideas about sexuality and the family.
Cardinal Sean O'Malley, 68, is a favourite in Boston where he came in and restored the Church's credibility in the midst of a horrific clergy child abuse scandal. A Capuchin Franciscan, he would be the first pope in many moons to wear sandals, have a beard and belong to a religious order.
Reporter John Allen says O'Malley's simplicity is drawing interest in the Italian press because of weariness over the Vatican's reputation for intrigue and power games.
O'Malley has said that the support of many Catholics for the Democratic Party "borders on scandal" because of the party's support for abortion and opposition to pro-life groups.
Cardinal Ordilo Pedro Scherer, 63, is archbishop of Sao Paulo, Brazil's largest diocese and one beset with a host of social problems, ranging from extreme poverty to crime to lack of running water.
Always willing to state the Church's stand on issues, he writes on his diocesan website and in the mainstream press. He has been openly critical of Pentecostal churches which, while responding to people's yearning for God, also serve to enrich their leaders.
Scherer has worked to strengthen the Catholic identity of Sao Paulo's Catholic university. If the cardinals look outside Europe for a new pope, Scherer could be near the top of their list.
Cardinal Jorge Bergoglio of Buenos Aires, Argentina, was the runner-up in the 2005 conclave, placing second on all four ballots with as many as 40 votes.
At 76, Bergoglio is perhaps too old to be given serious consideration, but he is more than a year younger than Cardinal Joseph Ratzinger was when he was elected pope.
He is a strong administrator and has good pastoral skills. Despite his strong intellect, Bergoglio is known for emphasizing the simplicity of the Gospel.
The Jesuit has been outspoken on a wide range of issues in Argentina, but is nevertheless considered to have a low profile in the media.
Cardinal Angelo Bagnasco, 70, is archbishop of Genoa and president of the Italian bishops' conference.
In that role, Bagnasco has been an outspoken opponent of abortion and legal recognition of cohabiting couples.
As a result, he received death threats from gay rights activists and was under police protection for several months.
A bishop for 15 years, Bagnasco has been a staunch defender of Pope Benedict, defending his controversial remarks at Regensburg, Germany, as well as his decision to lift the excommunications of four bishops of the Society of St. Pius X.