The Pope is holding a rare meeting with more than 100 cardinals from around the world for discussions on policy.
Religious freedom - the persecution of Christians in some countries and a dispute with China - and the clerical sex abuse scandal are on the agenda.
They will also discuss the decision to invite disaffected Anglican bishops and priests to join the Catholic Church.
The talks will be followed by the elevation of 24 new cardinals by Pope Benedict at a ceremony on Saturday.
Some cardinals have criticised the attention given to the sex abuse scandal.
"I'm tired of talking about this topic. I've had it up to here," Mexican cardinal Javier Lozano Barragan told reporters on the margins of the talks.
"It's a real media storm," he said.
Vatican spokesman Fr Federico Lombardi said no major developments were expected at Friday's talks.
This is the third consistory - or assembly of cardinals - of Pope Benedict's tenure, which began in 2005.
All 179 cardinals would only gather for a conclave - the meeting following the death or abdication of a pope to elect his successor.
But Pope Benedict has been attempting to create more opportunities for the cardinals to discuss important issues.
The event has been described by analysts as a pre-conclave, enabling the cardinals to see who could potentially succeed the German Pope.
They are also discussing religious freedom for Christians, following a recent rise in attacks on Christians in Iraq and a row with China over the ordination of bishops without papal approval.
On Saturday, a Chinese bishop, the Rev Guo Jincai, is due to be ordained in the city of Chengde, in Hebei province. He is a member of the state-backed church which does not recognise the pope.
The Vatican says it is disturbed by reports that bishops loyal to Pope Benedict are being forced to attend the ceremony.
"If these reports are true, then the Holy See would consider such actions as grave violations of freedom of religion and freedom of conscience," Fr Lombardi said in a statement.
The Vatican and China have had no diplomatic ties since the 1950s, when Beijing expelled foreign clergy, but their relationship had been improving in recent years.
The Pope's decision to welcome clerics who have defected from the Anglican Church - including those who are married - will also be discussed by the cardinals.
Benedict XVI has created a special enclave in the Roman Catholic Church for Anglicans unhappy with issues including the decision to let women and gay men become bishops. Five bishops have said they will convert under the scheme.