«Let us now pray for the success,» Cardinal Aloysius Ambrozic, archbishop of Toronto, told volunteers carrying flags from countries that will be represented at the event.
«Lord, hear our prayer,» a chorus responded, gathered under a hot sun in Exhibition Place, where the WYD opening Mass will be held.
The Mass with the volunteers was held Saturday in the presence of the WYD cross, which has traveled throughout Canada in recent months.
Over the next few days, some 20,000 volunteers, dressed in blue T-shirts and displaying photo identification, will assist the hundreds of thousands of young people arriving in the Greater Toronto area.
WYD will end next Sunday with a Mass celebrated by John Paul II.