On Wednesday, the red-hatted "princes of the Church" started the heavily ritualised process of choosing a new leader for the world's 1.4 billion Catholics. In the evening, black smoke billowed from a specially-installed chimney visible from St Peter's Square to signal an inconclusive ballot.
No pope in modern times has been elected on the first attempt, so that outcome was widely expected. However, given recent history, a final result is possible from the second day on Thursday, when up to four voting rounds can occur.
A record 133 cardinals from 70 countries - including Australia's Ukraine-born Cardinal Mykola Bychok - are involved in the secret ballot, up from 115 from 48 nations in the last conclave in 2013 - growth that reflects efforts by the late Pope Francis to extend the reach of the Church during his 12-year tenure.
Argentine-born Francis, who died in April, was elected at the end of the second day, after five rounds of voting. Eight years earlier, it also took two days but only four votes to elevate Germany's Benedict XVI to the papacy.
White smoke would signal the election of a new Church leader.
There are no clear favourites, although Italian Cardinal Pietro Parolin, the Vatican's number two under Francis, and Filipino Cardinal Luis Antonio Tagle are considered the front-runners.
Suppose it becomes obvious that neither can obtain the necessary two-thirds majority. In that case, votes are expected to shift to other contenders, with the electors possibly coalescing around geography, doctrinal affinity or common languages.
Other potential "papabili" - papal candidates in Italian - are France's Jean-Marc Aveline, Hungary's Peter Erdo, American Robert Prevost and Italy's Pierbattista Pizzaballa.
With AAP.
