The Assembly is the "supreme legislative body" of the WCC, and meets every seven years. The formal purpose of the Assembly is to review programmes and determine the overall policies of the WCC, as well as to elect presidents and appoint a Central Committee which serves as the chief governing body of the WCC until the next assembly.

Alongside the committee work and business sessions for the delegates, assemblies are also times of celebration and sharing for the many thousands of other visitors at the event.

A central element of assemblies for all participants is the worship life, where the community gathers for prayer and meditation, drawing on the diverse spiritual experience of the churches around the world.

The WCC's 9th assembly, held in Porto Alegre, Brazil from 14-23 February 2006, was an intense period of encounter, prayer, and celebration - in morning and evening worship, 90 Bible study groups, and in the 200 workshops and other events making up the assembly’s parallel mutirão. On another level, the in-depth work done by the Assembly on themes and issues, structures and relationships is likely to impact the WCC fellowship and the wider ecumenical movement for a long time to come.

At the end of the assembly, participants prayed, as they had done at the beginning of the ten-day event : "God, in your grace, transform the world". The prayer – that was also the assembly theme - was echoed by a message from the Assembly which ended : "Transform us in the offering of ourselves so that we may be your partners in transformation  to strive for the full, visible unity of the one Church of Jesus Christ, to become neighbours to all, as we await with eager longing the full revelation of your rule in the coming of a new heaven and a new earth."

Half a century after the official foundation of the WCC, its member churches renewed their commitment to stay together, and delegates promised to remain in solidarity with their African hosts.

The Assembly decided to set up a commission on the participation of the Orthodox churches in the WCC. It backed the creation of a "Forum of Christian Churches and Ecumenical Organizations" which could extend the ecumenical outreach far beyond WCC member churches. 

Delegates and assembly visitors participated in more than 600 contributions to a three-day "Padare" in which subjects ranged from Evangelical-Orthodox dialogue to human sexuality. It was preceded by a Decade Festival of churches in solidarity with women.