[Updated at 4:24 a.m. ET]
Dignitaries in St. Peter's Square for the Inauguration Mass include European Union leaders Jose Manuel Barroso and Herman Van Rompuy; and President Cristina Fernandez de Kirchner of the pope's native Argentina. Zimbabwean President Robert Mugabe, also present, is subject to an EU travel ban but is allowed to visit the continent for religious events and international conferences.
[Updated at 4:21 a.m. ET]
In the tomb of St. Peter, deacons of the church will collect two symbols of the papacy: the fisherman's ring and the pallium (a scarf-like cloth).
[Updated at 4:19 a.m. ET]
Pope Francis spent about 17 minutes circling St. Peter's Square in his open-topped car before going into St. Peter's Basilica.
[Updated at 4:18 a.m. ET]
Inside St. Peter's Basilica, Francis will visit St. Peter's tomb.
[Updated at 4:12 a.m. ET]
Zimbabwe's controversial President Robert Mugabe seen among the dignitaries.
[Updated at 4:07 a.m. ET]
Francis continues to wear the simple iron cross that he wore as a cardinal and that he wore when he first appeared to the world as pope.
[Updated at 4:03 a.m. ET]
Francis has at least a dozen security officers in suits walking alongside his car as he circles St. Peter's Square before his Inauguration Mass. The pope stops to kiss babies.
[Updated at 3:57 a.m. ET]
Francis stepped out of his car on St. Peter's Square to kiss the head of a man with a physical disability.
[Updated at 3:51 a.m. ET]
Francis has entered St. Peter's Square in a Jeep to greet the throng of believers, tourists, religious dignitaries and heads of state gathered there for the Mass to inaugurate him bishop of Rome.
[Updated at 3:40 a.m. ET]
Just in time for the inauguration comes a survey that finds that American Catholics are very enthusiastic about the choice of Pope Francis to head the Roman Catholic Church.
St Peter's Square normally holds about 100,000 people
Vatican spokesman the Rev. Federico Lombardi says that if the Square and Via Conciliazione are full, the crowd is about 250,000.
There will be 132 delegations from around the world, including six reigning sovereigns and 31 heads of state.