The Roman Catholic Church has issued guidance for future priests to have psychological tests to weed out those unable to control their sexual urges.
A senior churchman said a series of sex scandals had contributed to the rewriting of the guidelines.
The authors said screening would help avoid "tragic situations" caused by what they termed psychological defects.
The guidance says the voluntary tests should also aim to vet for those with "deep-seated homosexual tendencies".
Among other traits that might make a candidate unsuitable for the priesthood, the advice lists "uncertain sexual identity," "excessive rigidity of character" and "strong affective dependencies".
The document also makes reference to heterosexual urges.
Seminarians should be barred if testing makes it "evident the candidate has difficulty living in celibacy: That is, if celibacy for him is lived as a burden so heavy that it compromises his affective and relational equilibrium", it says.
The advice stipulates priests must have a "positive and stable sense of one's masculine identity".
The document, approved by Pope Benedict XVI and made public on Thursday, stresses that the screening must always have the candidate's consent.
The Catholic Church has been rocked by a series of sex scandals in recent years involving paedophile priests, notably in the US, Latin America and Europe, triggering lawsuits that have cost hundreds of millions of dollars in settlements.
And a seminary in Austria was shut down in August 2004 after revelations that students openly indulged in homosexual conduct.
Gay rights groups have accused the Church of using homosexuals as scapegoats for abuse scandals.
The Survivors Network of Those Abused by Priests (SNAP), a US-based group of victims of sexual abuse, said the revised guidelines did not go far enough.
"Catholic officials continue to fixate on the offenders and ignore the larger problem: The Church's virtually unchanged culture of secrecy and unchecked power in the hierarchy," it said in a statement.
"These broader factors are deeply rooted in the Church and contribute heavily to extensive and ongoing clergy sex abuse and cover up."