This work will analyze the lay participation and contribution in the work of the Second Vatican Council, in three stages that can be distinguished as follow: 1) Remote preparation for Vatican II, especially in the work of lay movements. 2) Immediate preparation: the collaboration of lay people in the work of the preparatory commissions, and the sharing of the laity in the wider task of bringing the whole Church into a « state of Council ». 3) Participation of lay people during the actual celebration of the Council.