1. From the day of Pentecost, after the coming of the Holy Spirit, the Church of Christ has always faithfully come together to celebrate the paschal mystery on the day called " the Lord's Day" in memory of the Lord's resurrection. In the Sunday assembly the Church reads in all the Scriptures those things that concern Christ  and celebrates the eucharist as the memorial of the death and resurrection of the Lord until he comes.
2. But a complete celebration of the Lord's Day is not always possible. There have been and still are many of the faithful for whom "because of the lack of a priest or some other serious reason, participation in the eucharistic celebration is not possible." 
3. In some regions, after their first evangelization, the bishops have put catechists in charge of gathering the faithful together on Sunday and, in the form of a devotional exercise, of leading them in prayer. In such cases the number of Christians grew and they were scattered in so many and such widely separated places that a priest could not reach them every Sunday.
4. In other places the faithful were completely blocked from gathering on Sunday, either because of the persecution of Christians or because of other severe restrictions of religious freedom. Like the Christians of old, who held fast to the Sunday assembly even in the face of martyrdom , the faithful today, even when deprived of the presence of an ordained minister, also strive to gather on Sunday for prayer either within a family or in small groups.
5. On other grounds today, namely, the scarcity of priests, in many places not every parish can have its own eucharistic celebration each Sunday. Further, for various social and economic reasons some parishes have many fewer members. As a consequence many priests are assigned to celebrate Mass several times on Sunday in many, widely scattered churches. But this practice is regarded as not always satisfactory either to the parishes lacking their own pastor or to the priests involved.
6. In some local Churches, then, because of the conditions indicated, the bishops have judged it necessary to arrange for other Sunday celebrations in the absence of a priest, so that in the best way possible the weekly gathering of the faithful can be continued and the Christian tradition regarding Sunday preserved.
It is by no means unusual, particularly in mission territories, for the faithful themselves, aware of the importance of the Lord's Day and with the help of catechists and religious, to gather to listen to the word of God, to pray, and , in some cases, even to receive communion.
7. The Congregation for Divine Worship has considered these matters, reviewed the documents already published by the Holy See , and acceded to the wishes of the conferences of bishops. Therefore the Congregation regards it as opportune to recall elements of the teaching on the meaning of Sunday, to lay down the conditions for the lawfulness of such celebrations in dioceses, and to provide guidelines for carrying out such celebrations correctly.
It will be the responsibility of the conferences of bishops, as circumstances suggest, to determine these norms in greater detail, to adapt them to the culture and conditions of their people, and to report their decisions to the Apostolic See.