Communion under both species means receiving both the consecrated bread and the consecrated wine at Mass. The faithful usually have the opportunity to receive the consecrated bread, or host, at Mass, while they may or may not have the opportunity to receive consecrated wine from the chalice. When they do, they are said to be able to receive the Eucharist “under both species” or “under both kinds.”

While the consecrated bread is called “the Body of Christ” and the consecrated wine is called “the Blood of Christ,” as is evident from the words of the consecration, the fact is that the Body, Blood, soul, and divinity of Christ is present under either form. So when we receive the sacred host, we have “fully communicated”—in other words, receiving from the cup or chalice doesn’t add something that was lacking in the host. And the converse is true: We have received the “whole Christ” when we receive only from the cup, as may happen in the case of gluten intolerance or other unusual circumstances.

There was a time during the Middle Ages when the question of receiving under both species was a point of controversy. The Church formally determined, as noted above, that Christ is fully present under the appearance of either species, so that receiving under one species was sufficient. For that reason, the prevailing practice in the West ever since has been that the faithful receive only the sacred host (see generally Catechism of the Catholic Church, no. 1390).

However, in recent decades the Church has encouraged the reception of Communion under both species. The General Instruction of the Roman Missal (GIRM), as adapted for use in the United States, explains:

“Holy Communion has a fuller form as a sign when it is distributed under both kinds. For in this form the sign of the Eucharistic banquet is more clearly evident and clear expression is given to the divine will by which the new and eternal Covenant is ratified in the Blood of the Lord, as also the relationship between the Eucharistic banquet and the eschatological banquet in the Father's Kingdom” (no. 281).

When Communion is available under both species, the individual communicant may decline to receive from the cup. However, the Church does warmly encourage reception under both species.

Lastly, it should be noted that practical difficulties may arise when giving Communion under both species. The lack of a sufficient number of trained ministers as well as the sheer size of the congregation may make the practice unduly cumbersome. The decision to allow Communion in a particular situation is left to the pastor’s prudential judgment, based on Church guidelines as well as any further direction from his bishop.

In any event, since Christ is fully present under the appearance of wine, the sacred species at all times needs to be handled with utmost care and reverence.

The U.S. bishops have further noted that if extraordinary ministers of Holy Communion are called upon to assist with Communion under both kinds, they should not approach the altar before the priest has received Communion.

For more information, see:

General Instruction of the Roman Missal (especially chapter IV, part IV)

Extraordinary Ministers of Holy Communion at Mass

Norms for the Distribution and Reception of Holy Communion Under Both Kinds in the Dioceses of the United States of America

Seven Questions on the Distribution of Holy Communion Under Both Species

Holy Communion Under Both Species (CUF Faith Fact)