A distinction is made between the insignia of ecclesiastical and sacerdotal office in the hierarchy and the functionally and symbolically significant liturgical robes. After the so-called barbarian invasions of the Roman Empire from the 4th century on, fashions in secular dress changed, and thus the clergy became distinct in matters of dress from the laity. Certain robes indicate a position in the hierarchy, while others correspond to function and may be worn by the same individual at different times. The most important vestment among the insignia is the stole, the emblem of sacerdotal status, the origin of which is the ancient pallium. The stole originally was a draped garment, then a folded one with the appearance of a scarf, and finally, in the 4th century, a scarf. As a symbol of jurisdiction in the Roman Empire, the supreme pontiff (the pope, bishop of Rome) conferred it upon archbishops and, later, upon bishops as emblematic of their sharing in the papal authority.

The distinctive garb of the liturgical celebrant is the chasuble, a vestment that goes back to the Roman paenula. The paenula also was the Eastern Orthodox equivalent of the chasuble, the phelonion, and perhaps also the cope (a long mantlelike vestment). In its earliest form, the paenula was a cone-shaped dress with an opening at the apex to admit the head. Because ancient looms were not wide enough to make the complete garment, it was made in several parts sewn together with strips covering the seams. These strips, of contrasting material, developed into the orphrey (embroidery), on which much attention was later lavished. Next in the hierarchical order after the priesthood were the diaconate and subdiaconate, whose characteristic vestments were, respectively, the dalmatic (dalmatica), a loose-fitting robe with open sides and wide sleeves, and the tunic (tunica), a loose gown. A priest wore all three, one over another. Under these he wore the alb (a long white vestment), held round the waist by a girdle, and around the neck the amice (a square or oblong, white linen cloth), with the maniple (originally a handkerchief) on the left arm. Although the deacon used a stole, the subdeacon did not. In the formative period of liturgical dress, these practices were in the process of becoming normative. During the 9th–13th century the norms now familiar were established. The chasuble became an exclusively eucharistic garment. The cope, excluded from the Eucharist, became an all-purpose festive garment.

Next in importance to the chasuble is the cope, a garment not worn during the celebration of the mass but rather a processional vestment. It is worn by the celebrant for rites of a non-eucharistic character, such as the Asperges, a rite of sprinkling water on the faithful preceding the mass. The origins of the cope are not known for certain by liturgical scholars. According to one theory, it derives from the open-fronted paenula, just as the chasuble derives from the closed version of the same garment. (The subsequent wide divergence between the two vestments need not preclude a common origin.) Unlike the chasuble, the form of which has never stopped changing, the evolution of the cope was complete before the end of the Middle Ages. Cope chests, based on the quadrant of a circle and designed to preserve the embroidered surfaces by keeping the copes flat, were a common feature of medieval cathedrals. When it is worn, the two sides of the garment are held together by a morse (a metal clasp). The cope occupied an intermediate position between liturgical and nonliturgical vestments, the most important of which was the cassock, the normal dress of the priesthood outside church ceremonies. When engaged in religious ceremonies, the officiant would wear the liturgical vestments over his cassock.

The tiara, the papal diadem or crown apostolic, emerged in the early medieval period; and the mitre (the liturgical headdress of bishops and abbots), the most conspicuous of the episcopal insignia, began as a mark of favour accorded to certain bishops by the supreme pontiff at a somewhat later date.

Like the cope, the surplice (a white outer robe) entered liturgical usage in the Middle Ages as a late modification of the alb. By the 14th century its present role as a choral or processional garment was established. With the passage of time, the length of the garment grew progressively shorter.

The surplice was also associated with the monastic orders, but vesture distinguished only the order and not the kind of order. Eremitical (hermitic) monasticism allowed no standard form of dress to develop, and only communal monasticism, beginning with the Rule of St. Benedict in the 6th century, enabled standardization to become possible. Monastic dress included habit, girdle or belt, hood or cowl, and scapular (a long narrow cloth worn over the tunic). The salient characteristics of monastic dress have always been sobriety and conservatism. The orders proved even more retentive of archaic fashions than the hierarchy, and, in contrast to the deliberate splendour of ecclesiastical vestments, monastic dress was expressive of a renunciation of luxury. The contrast was functional in origin: the menial tasks of the monk related him sartorially to the peasant, whose humble avocations he often duplicated, rather than to the princes and prelates of the church, whose dress reflected the splendour of the ceremonies in which they engaged.

Because of the diversity of the monastic orders, only a summary account of their vesture may be given. The Benedictine mantle was black, fastened with a leather belt, but the Cistercians—reformed Benedictines—eschewed any dyed material and instead dressed in undyed woollen material, which was off-white in color. In the course of time this became white, a tacit relaxation of the earlier austerity adopted as a protest against “luxury.” Carthusians, a contemplative order founded in the 11th century, likewise wore white. In the 13th century the mendicant orders (friars) emerged. The Franciscans, founded by St. Francis of Assisi, first used a gray habit, which in the 15th century was exchanged for a brown one; in spite of this change they continued to be known as the Grey Friars. The Carmelites, an order founded in the 12th century, became known as White Friars. Dominicans, founded by St. Dominic from Spain, adhered from the beginning to a black robe over a white gown. Canons regular (communal religious persons living under vows), although ordained, lived like the orders under a rule, and the Augustinians (several orders following the Rule of St. Augustine) are styled Black Canons in contradistinction to the Premonstratensians, or White Canons, an order founded by St. Norbert in the 12th century. Because the office (prescribed prayers) took up so much of a monk’s time, his choir robes were almost as important as his day clothes. Surplices were worn in choir with an almuce over; this last was a lined shoulder cape designed to help the wearer resist the cold of medieval churches.

Nuns’ costumes were similar to those of monks, the chief difference consisting in the replacement of the hood by a wimple (collar and bib) and head veil. Habits are white or black or mixed, and this remained unaltered until the 17th century, when the Sisters of St. Vincent de Paul introduced blue. The Missionaries of Charity, founded by Mother Teresa in 1950, wear a distinctive white sari with three blue stripes. These exceptions remained unique; nuns’ habits retained a markedly medieval aspect until reformed by the Second Vatican Council (1962–65). Many modern nuns are no longer required to wear a habit, especially those in active, rather than contemplative, service.

The cassock has its origin in the caracalla, a robe favoured by the Roman emperor Bassianus (reigned 211–217), who came to be known as Caracalla because of the garment he habitually wore. Worn by the clergy as early as the 5th century, it became in time the standard day wear for prelates and priests, hierarchical rank being indicated by color: bishops, archbishops, and other prelates wore purple; cardinals, red; the pope, white; and ordinary clergy, black.