Question:
Answer:
There is no strict rule regarding the choice of the eucharistic prayer at Mass, except for Eucharistic Prayer IV, which may be used only on days that do not have a strictly proper preface.
There are, however, norms guiding the choice of the Eucharistic Prayer found in number 365 of the General Instruction of the Roman Missal. Eucharistic Prayer I, called the “Roman Canon,” has pride of place and is the only one of which it is said it “may always be used.” This is on account of its great authority as the only eucharistic prayer in use in the Roman rite for at least a 1,500 years. It is, strangely perhaps, the least used now.
Eucharistic Prayer II is regarded as suitable for weekday Masses, probably on account of its convenient brevity, called in the instruction “its particular features.” It is perhaps the most frequently used eucharistic prayer, even on Sundays in some places. Blessed Paul VI lamented that his permission of its use had led to the abuse of using it because it is shorter than the others!
Eucharistic Prayer III is suitable especially for Sundays, and, I add, it conveniently has a place for the commemoration of the saint of the day or of the patron of the place or community.
Eucharistic Prayer IV may be used on any day that does not have a strictly proper preface: so Sundays in Ordinary Time, and any feasts or memorials or ferial days that have only a common preface. Thus, it can be used most days of the year. This prayer is not usually used at funeral Masses, because it does not have any text that mentions the deceased by name. It is very beautiful and is also less used than the others, perhaps the least commonly used of all the four.
As for the many other eucharistic prayers approved for children’s masses and for special needs and occasions and for reconciliation, these should be used only in their limited thematic contexts, not generally at Sunday Masses, for example. In any case, the instruction makes clear that the four eucharistic prayers are the norm in the Ordinary Form of the Roman rite, and that among them Eucharistic Prayer I has a certain pride of place.