In the Orthodox Eastern churches, ordinary parish clergy are married, but monks, nuns, and bishops are celibates. In the West, celibacy was common among the parish clergy beginning the 3d cent.; as time passed, the Holy See became adamant in opposing the marriage of the secular clergy (see orders, holy). By the early Middle Ages, marriage of the clergy had fallen into disrepute; church reformers aimed at concubinage and violations of the laws of chastity rather than of marriage. In the 12th cent. the most stringent laws were enacted, and by the time of the Reformation popular opinion tolerated neither concubinage nor marriage in the clergy. Protestantism rejected voluntary celibacy as an ideal.

The Roman Catholic Church in the Roman rite allows no sacerdotal marriage, but the clergy of Eastern rites united with the Holy See are often married before ordination. Some married priests from other religions or rites have converted to Catholicism and been accepted, but not all dioceses have permitted these priests to practice. Although recent popes and various national groupings of bishops have insisted on the retention of celibacy for priests, there has been considerable pressure in the United States and Europe in support of voluntary marriage for the clergy. A standard defense of the Western discipline of celibacy for parish priests is that marriage would prevent the priest from giving his complete attention to his parish; critics complain that unmarried clergy are unfit to give counsel on marital and sexual problems. Since the Second Vatican Council, the Roman Catholic Church has restored the office of deacon to a prominent place in the ministry and accepts married men into it.