The subdeacon is vested in a sticharion with an orarion tied around his waist, up over his shoulders (forming a cross in back), and with the ends hanging down in front, tucked under the section around the waist. Often, ordained subdeacons will wear their orarion crossing in front and in back (forming a cross on either side) to separate themselves from acolytes (servers) who wear theirs as in the former case. Like readers, subdeacons are permitted to wear a cassock, although many only do so when attending services. In the United States a clergy-shirt will sometimes be worn instead, and is commonly worn buttoned but with no collar or collar-tab to indicate a rank lower than deacon.
The other major orders — those of deacon, priest, and bishop — are considered of divine institution and part of the sacrament of Holy Orders, whereas the subdiaconate and the minor orders were considered of ecclesiastical institution, created by the Church. Thus, a subdeacon did not receive the laying on of hands at his ordination. Instead, the bishop handed to him an empty chalice and paten, his vestments, cruets of wine and water, and the Book of the Epistles. But, as the recipient of a major order, a subdeacon could not contract marriage, and any breach by him of the obligation to observe celibacy was classified as a sacrilege (cf. canon 132 of the 1917 Code of Canon Law). Canon 135 of the same Code of Canon Law obliged him to say all the canonical hours of the Divine Office (Liturgy of the Hours or Breviary).
The roles of a subdeacon at Solemn High Mass included those of crucifer (only on certain occasions such as Palm Sunday, requiems and Holy Saturday), singing the Epistle, carrying the Book of Gospels back to the celebrant after the deacon has sung the gospel (the deacon carries the book in the Gospel procession to the place where the gospel is proclaimed) and holding it while the deacon sang the Gospel, and assisting the priest or deacon in setting the altar. The subdeacon's specific vestment was the tunicle, in practice almost indistinguishable in form from the deacon's dalmatic (the tunicle was sometimes somewhat smaller than the dalmatic, or had slightly less elaborate decoration, but this was often unnoticeable by the average lay churchgoer). He wore a maniple, until this vestment was made optional by Pope Paul VI with the instruction Tres annos abhinc. Unlike the deacon, priest and bishop, the subdeacon never wore a stole. He also wore a humeral veil while holding the paten during a large part of Solemn High Mass, from the offertory to the Our Father; and, if the chalice and paten with host were not already on the altar, he also used the humeral veil when bringing these to the altar at the offertory.
With effect from 1 January 1973, the apostolic letter Ministeria quaedam of 15 August 1972 decreed that the functions that in the Latin Church had been assigned to the subdeacon should from then on be carried out by the instituted ministers (not members of the clergy) known as lectors and acolytes:
Traditionalist Catholic organizations such as the Priestly Fraternity of St. Peter, the Institute of Christ the King Sovereign Priest and the Personal Apostolic Administration of Saint John Mary Vianney have been permitted to retain the subdiaconate, as well as other pre-1970 forms of the Roman Rite liturgy. The controversial Society of St. Pius X (SSPX) and other traditionalist Catholic bodies in dispute with the Holy See, such as sedevacantists, have also retained the subdiaconate, without seeking authorization to do so.
Thus, within the Latin-Rite Catholic Church, the term "subdeacon" now applies only to those ordained to that rank within one of these groups and to acolytes in countries where the Episcopal Conference has chosen to give them the name of subdeacon. Otherwise, it is a historical reference to persons and events of the pre-1973 period.
The entrusting to readers and acolytes of all the functions that in the Latin Rite once belonged to subdeacons does not affect the Eastern Catholic Churches.