The main opposition group declared itself Zimbabwe's new ruling party and convened what it called a session of parliament in defiance of President Robert Mugabe.
Movement for Democratic Change leader Morgan Tsvangirai asked his party's lawmakers to stand for a minute's silence for the more than 50 people who have died in violence since March elections.
He promised "a new and different era of governance."
The opposition won 110 of the 210 seats in parliament. Tsvangirai faces Mugabe in a June 27 runoff for president.