Pope Benedict XVI has given his first traditional Sunday blessing to the faithful from the same apartment window used by his predecessor.
The Pope called for unity in the Christian world
St Peter's square was packed with tens of thousands of pilgrims, who the Pope addressed in Italian and Spanish.
He also wished Orthodox Christians a happy Easter, and mentioned the need to promote Christian unity in the world.
In delivering his blessing on May Day, Benedict XVI also called for worker's rights to be respected.
"I address you, my very dear brothers and sisters, for the first time from this window that the beloved figure of my predecessor made familiar to countless people in the entire world," he said.
The pontiff also made a reference to violence-stricken Togo, where many have died in riots that followed controversial presidential elections.
Vatican Radio earlier said the event would be emotional for the new Pope. No-one had appeared at the window since 30 March - three days before John Paul died.
Pope Benedict was elected on 19 April and moved into his residence - the Apostolic Palace - on Saturday.
In line with Vatican tradition, the papal apartment was sealed after the death of John Paul on 2 April.
On Saturday, the Pope also approved the cardinals' election of Cardinal Angelo Sodano as dean of the College of Cardinals, the position that Benedict XVI held until he became Pope.
Cardinal Sodano is also the Vatican's secretary of state.
The Vatican has also announced that the first head of state to visit the new Pope will be Italy's President Carlo Azeglio Ciampi next Tuesday.