Pope John Paul has appointed 31 new Cardinals.
It was not immediately clear how many were under the age of 80 and would therefore be able to take part in naming his successor.
Before today's appointments there was a total of 166 Cardinals, 109 of whom are electors because they are still under 80.
The usual maximum number of Cardinal electors is 120, but the Pope said he had decided to go over that limit, as he did the last time he named new Cardinals in 2001.
The consistory ceremony for the new cardinals will be held on October 21.
The Pope, addressing pilgrims in St Peter's square, said he was keeping the name of one cardinal 'in pectore' (secret).
The new cardinals include seven Vatican officials, as well as prelates from Italy, Nigeria, France, Sudan, Spain, the United States, Scotland, Brazil, Ghana, India, Croatia, Guatemala, Hungary, Canada, Switzerland, Belgium, the Czech Republic and his native Poland.