People with "deep-seated homosexual tendencies" cannot become priests in the Roman Catholic Church, the Vatican says in a new document.
People involved or supporting the "so-called gay culture" are also barred from the priesthood, it says.
Pope Francis has approved the document, 'The Gift of the Priestly Vocation', from the Congregation for the Clergy.
Becoming a priest is a "journey of discipleship" which begins at baptism, the document explains. Priesthood is a gift from God to the Church and the world.
Priests should be "missionary disciples". They must be "faithful to celibate chastity" and must cultivate "authentic and filial devotion to the Virgin Mary".
The "possibility of a candidate having homosexual tendencies" must be examined before admission to seminary.
The document says some homosexual tendencies, such as those of adolescence, might be transitory. But these must be overcome for "at least three years" before ordination to the diaconate.
A man who practises homosexuality or has homosexual tendencies must be dissuaded by his confessor. The document says it would be "gravely dishonest" for a homosexual man to pretend not to be gay in order to proceed to ordination.
"The Church, while profoundly respecting the persons in question, cannot admit to the seminary or to holy orders those who practise homosexuality, present deep-seated homosexual tendencies or support the so-called 'gay culture.' Such persons, in fact, find themselves in a situation that gravely hinders them from relating correctly to men and women. One must in no way overlook the negative consequences that can derive from the ordination of persons with deep-seated homosexual tendencies."
In addition to gay priests being banned, most priests cannot marry. Women are also barred from the Catholic priesthood.
The Catholic Church is suffering a serious shortage of priests, in particular in the West. By 2014, nearly 50,000 parishes worldwide were surviving without a priest. There are currently more than 400,000 Catholic priests worldwide. One area of growth however is in "mature" vocations where men who already have a career behind them experience a call to the priesthood.
Every year the Church sets aside Good Shepherd Sunday, the fourth Sunday of Easter, as a day of prayer for more vocations.
The document effectively reiterates the Church's traditional position, last stated in 2005.
Rev James Martin, a Jesuit priest and America magazine editor, told the Washington Post: "Not much has changed. The people who were open to accepting healthy gay men into the seminaries will still do it. It does not negate the fact, nor could it, that there are thousands of healthy and hard-working and holy and celibate gay priests throughout the world."
