115 cardinals from around the world are at the Vatican to select a new Pope.
The conclave to name the next leader of the Roman Catholic Church begins Tuesday in the Sistine Chapel.
After the votes are taken, the ballots are burned in a stove.
Black smoke means there is no decision -- white smoke signals a Pope has been chosen.
Vatican spokesman Father Tom Rosica says the cardinals could vote Tuesday night.
"Regarding the first smoke that we might see, the last time it was about eight o'clock, shortly after eight o'clock. That's a long time, because there's the prayer, there's the voting, there's the meditation, the voting. Don't expect anything before eight o'clock. It's unlikely that there will be white smoke on the first ballot. However, be aware that around eight o'clock we'll probably see the first signs of smoke coming from the chimney," Father Tom Rosica, the Vatican Spokesman said.
It takes two-thirds of the vote, necessary for victory.
More than 5,600 journalists are accredited to cover the selection of the new pope, according to the Vatican.