A new pope is elected by the College of Cardinals in Rome, who gather under Michelangelo's famous frescoes in the Sistine Chapel under strict security measures. Only cardinals under the age of 80 can vote, and in recent times the number of voting cardinals has been kept to roughly 120.
In September 2003, however, an ailing Pope John Paul II strengthened his influence over the choice of his successor by naming 31 new cardinals. The latest appointments brought to at least 117 the number of cardinals under 80.
Each voting cardinal writes the name of his choice for pope on a ballot and is asked to disguise his handwriting to avoid letting others know who is supporting whom.
If no one receives the required two-thirds-plus-one votes, additional ballots take place immediately. There can be only four ballots in a single day, and if after three days the cardinals still haven't selected anyone, the voting sessions can be suspended for a day of prayer and discussion.
In 1800, the balloting conclave lasted 3 ½ months, and in 1831, 54 days, but in modern times, conclaves usually last, at most, only a few days.
When the process is over, the Vatican tells the world of the election of a new pope by sending up puffs of white smoke from the chimney of the Sistine Chapel.