Editor's note: This article originally appeared in 2003, when Pope John Paul II was undergoing a serious illness. It has been slightly updated.
What will be the procedure for selecting the next pope, the 264th successor to St. Peter?
According to centuries-old tradition, the papal election will be handled entirely by the Sacred College of Cardinals. The college is technically supposed to consist of a maximum of 120 cardinals, though Pope John Paul II has bent this rule by adding a few more (the current cardinal count is 135). Fifteen to 20 days after the pope's death, the cardinals will convene in the Sistine Chapel, in a secret meeting known as the conclave. There, they'll be handed strips of paper emblazoned with the Latin words "Eligo in summum pontificem"—I elect as supreme pontiff. Each cardinal will write down the name of the fellow cardinal he'd like to see elevated to pope and place the ballot in a chalice. (Although the name of any Catholic man can technically be submitted, cardinals, almost without exception, vote for other cardinals.) A cardinal is not supposed to vote for himself. And per a 1975 rule change made by Pope Paul VI, cardinals 80 years old or greater are barred from voting.
The votes will be tabulated by the camerlengo (currently Cardinal Eduardo Martinez Somalo of Spain), head of the college and the man who manages the pope's secular affairs. An assistant will then bind the ballots together with a needle and thread. A victor must receive more than two-thirds of the votes, so it's unlikely anything will be decided after the first round of ballots. If the vote is inconclusive, the ballots will be mixed together with straw and burned in the fireplace; the black smoke that issues forth signals to outside observers that the election is still ongoing.
In past elections, the balloting continued until a candidate received a two-thirds majority. But in 1996, Pope John Paul II tweaked the rules when he promulgated the Universi Dominici Gregis. Aside from mandating that the cardinals could stay in the nearby Domus Sanctae Marthae (St. Martha's House) during the election (rather than in cubicles in the Apostolic Palace), the document also stipulates certain circumstances under which an absolute majority can suffice. Basically, if no decision is reached after three days, the conclave should take a one-day break. After the cardinals return, they should go through no more than 21 additional ballots, with a break for prayer and discussion after the seventh, the 14th, and the 21st. At that point, an absolute majority—that is, half the cardinals plus one—is all that's needed to tap the next pontiff.
Once the decision is made, the ballots will be burned sans straw; the resulting white smoke is the signal that a new pope has been successfully selected.
Explainer thanks Father Thomas J. Reese of America magazine.