BOB ABERNETHY, anchor: This weekend (July 8-9)--the third foreign trip of Pope Benedict XVI, a brief visit to Spain to attend the Church's World Meeting on the Family. Benedict has urged greater protections for the traditional family, which he says is besieged on many fronts. He has repeatedly called on Catholics to reaffirm their opposition to gay marriage, abortion, contraception and human embryo research.

That message is particularly challenging in Spain, once considered a European stronghold for the Roman Catholic Church. Today Spain, like the rest of Western Europe, has become increasingly secular, and the pope is deeply troubled about that. Just before the Spain trip, a prominent cardinal expressed the Vatican's concern that Europe has become "drunk from secularization." Saul Gonzalez has more from Madrid.

SAUL GONZALEZ: For centuries, Spain was a bastion of fervent Catholicism. Its church leaders created such religious orders as the Jesuits and Dominicans, while the country's explorers and missionaries spread Christianity across oceans and continents. However, in 21st-century Spain, as in the rest of Western Europe, the Catholic Church finds its spiritual and social influence in decline. It's estimated fewer than 20 percent of Spaniards now attend Mass regularly, and those who do are generally elderly. Blanca Castelleano still faithfully goes to Sunday services with a friend, but she acknowledges her congregation has dwindled over the years.

BLANCA CASTELLEANO (through translator): I think the majority of people are still moral, but they just don't pay much attention to religion, nor do they go to church. There just aren't many people who practice their faith anymore - at least it seems that way to me.

GONZALEZ: Many experts say the weakening of the Catholic Church in Spain is attributable to a rapid secularization of Spanish society, especially since the death of dictator Francisco Franco in 1975. Once one of Europe's most religiously and socially conservative countries, with Catholicism as the only state-recognized religion, Spain now has a reputation in Europe as "Sweden South." That's because of the country's openness about sex, the easing of divorce and abortion restrictions, the growth of a large immigrant Muslim population, and the emergence of a vocal gay and lesbian civil rights movement. It's a movement that scored a historic victory in 2005 with Spain's legalization of same sex marriage. Although the change was condemned by the Catholic Church, it had the support of both Spain's ruling socialist party and, according to polls, a majority of the country's citizens.

BEATRIZ GIMENO (Attorney, through translator): This is a very different country compared to the recent past, when the presence of the Catholic Church was total in every way.

GONZALEZ: Attorney Beatriz Gimeno is Spain's leading gay and lesbian rights leader and a frequent critic of the country's Catholic establishment.

Ms. GIMENO (through translator): When I started this struggle about 20 years ago, we were coming out of the Franco era, and homosexuality was still legally punished. You could actually go to jail for it. And in 20 years we have gone from a time when we could go to jail for being homosexualto where we can now marry and live normal lives.

GONZALEZ: Not all Spaniards, however, are happy about the speed and scope of change in their country in recent decades. They believe too many spiritual values have been replaced by secular ones, and they're starting to fight back. What's at stake in the struggle, they say, is the soul of Spain and Europe.

Father LEOPOLDO VIVES SOTO (Theologian and Spokesman, Catholic Church, through translator): Without a doubt, there's a culture war going on. The Catholic Church, and indeed Christian Europe, confront a huge and clear cultural challenge.

GONZALEZ: Father Leopoldo Vives Soto is a theologian and spokesman for the Catholic Church in Spain. Like other Catholic leaders, he believes European Catholicism is struggling against a destructive tide of secularism on the continent - one that Father Soto says jeopardizes European families and society.

Father SOTO (through translator): Sure, many people believe that the church is backward. It's not advanced and against social progress. But that depends on what your idea of progress is. Is it progress to have an abortion? Is it progress to have a pill for abortion? Is it progressive to have a divorce? The social affects of these kinds of things are terrible.

GONZALEZ: One of those effects, says Soto, is demographic. Spaniards, like other Europeans, have largely ignored the Vatican's ban on contraception in recent decades. That's helped lead to a sharp decline in birth rates on the continent. Spain's is one of the lowest in the world.