Pope Francis has published new guidelines on family life that argue the Church should show more understanding of modern realities.
The document, based on two Synods on the issue, was eagerly awaited by the world's 1.3bn Roman Catholics.
Entitled "On Love in the Family", it does not change Catholic doctrine.
But it opens the way for bishops in each country to interpret doctrine to suit their own culture, the BBC's religion correspondent reports.
It details the Pope's views on family life, marriage, contraception and bringing up children.
The document is the culmination of three years' work by the Pope.
The Pope had sent a questionnaire to families across the world asking them about their hopes and their fears.
Key quotes from On Love in the Family
"We have been called to form consciences, not replace to them."
"As for proposals to place unions between homosexual persons on the same level as marriage, there are absolutely no grounds for considering homosexual unions to be in any way similar or even remotely analogous to God's plan for marriage and family"
"I understand those who prefer a more rigorous pastoral care which leaves no room for confusion. But I sincerely believe that Jesus wants a Church attentive to the goodness which the Holy Spirit sows in the midst of human weakness."
Then he brought bishops and cardinals together for two Synods in Rome, at which he encouraged them to debate and even to disagree over issues that divide the Church in many countries.
Among the most divisive issues are offering communion to the divorced and remarried, contraception and the treatment of gay Catholics.
Our correspondent, Caroline Wyatt, says the lengthy document shows exactly where Pope Francis stands as he steps into the minefield of Catholic teaching on the family.
Family values in practice
The BBC spoke to four Catholic families - in the Philippines, Brazil, Ireland and Ghana - about how their family values relate to the teachings of the Church.
Louis Doe Atsiatorme from Ghana had to get a special dispensation from the Church before he could marry a Methodist.
Liberals had hoped he would tell the Church to show a more merciful attitude to those whose families do not conform to the current Catholic ideal.
Conservatives had maintained it would devalue the principle established by Jesus of marriage being indissoluble.
At the conclusion of the Synod last year, Francis castigated Church leaders who, he said, buried their heads in the sand over the issue. He argued that their adherence to rigid doctrine was over-riding their concern for the suffering of families.
It is a document in which the Pope performs a delicate balancing act, trying to ensure that he does not alienate traditionalists, nor those who wanted radical change, our religion correspondent says.
What the Pope says is likely to be claimed as a victory by both sides, with enough to satisfy both traditionalists and liberals - though it is likely to disappoint gay Catholics, who had hoped for more than greater pastoral understanding, she adds.