Now comes the hard part. With Pope John Paul II back in Rome after a five-day visit, responsibility for carrying out his call for Catholics to play a larger role in Cuban society falls to a local church whose mission has been severely circumscribed under communism for nearly 40 years.

As they left the open-air Mass that the pope celebrated Sunday in the Plaza of the Revolution in Havana, many Roman Catholics said they felt inspired and energized by his call to live their faith. But they also acknowledged that they were uncertain exactly how to do that."The Cuban church has already reaped fruits from this visit in the months preceding it, and will see even more afterward," Cardinal Jaime Ortega, the archbishop of Havana and president of the Cuban Conference of Bishops, said last week. Significantly, he predicted that the church here "will find a path toward greater social action" in areas where "the church can find the human being and extend a helping hand."

Indeed, through the charitable group called Caritas, the Roman Catholic Church in Cuba has already managed to gain a small but important point of entry into secular Cuban society.

More than 3,000 volunteers work in Caritas social welfare and aid programs that include distribution of medicine and food, activities that President Fidel Castro's government reserved exclusively for itself until a "special period" of economic austerity was decreed after the collapse of the Soviet bloc.

Obviously, the key figure in any future expansion of the church's role will be Ortega himself, who, as the pope repeatedly made clear during the visit here, enjoys the full backing and confidence of the Vatican. In fact, John Paul's last public act before boarding his plane back to Rome on Sunday night was to embrace Ortega in front of Cuban television cameras.

Support for Ortega and the Cuban church from "sister churches" in Latin America and North America was evident in preparations for the papal visit. Much of the material used to make Cuban and Vatican flags, as well as the bulk of the paper and equipment used to design and print everything from news releases to orders of worship, were donated by foreign dioceses led by cardinals or bishops close to Ortega.

As a result of other donations from abroad, the majority of Cuba's 11 dioceses now operate pharmacies that distribute, at no cost, medicines that either cannot be found at public hospitals or are available only at black market prices.

Many individual parishes offer free breakfast or lunch programs for children or the elderly, and some have even hired doctors to make calls on pensioners, ignoring rules forbidding physicians from working outside the state health system.

Ostensibly such activities are purely charitable in nature, which is why they have gained the reluctant acquiescence of the state, whose capacity to provide such services has diminished.

But, church officials said, the government has rejected proposals by Caritas to undertake programs to build housing, create jobs and grow food, fearing, according to diplomats, both a loss of control and prestige.

"The power of the Communist Party derives primarily from the monopoly control it maintains of all the goods and services that the ordinary citizen needs," said the envoy of a former Soviet-bloc country. "To the extent that church organizations can build their own independent networks to supply people with food and medicine, even that diminishes the authority of the party."

In each diocese, the church has also developed a network of monthly magazines and newsletters that are the only officially sanctioned private publications in a country where all other media outlets are under government control. These publications, bearing names like New Word or Truth and Hope, have limited circulation, but offer a diversity of views not found elsewhere not only on religious issues, but also pressing social and economic questions as well.

For example, New Word, the monthly of the Havana archdiocese, recently featured an essay titled "Variations on Economic Reform," a controversial topic here. An article by Dagoberto Valdes Hernandez in Vitral argues that Christians must learn "to think with our own heads, to say what we thinkand say if we consider it to be good and true."

Valdes, an agronomist, leads another important church initiative in his diocese, the Center for Religious and Civic Information. Nearly 2,000 people have attended a 10-week program the center offers on Christian ethics, including the principles of democracy.

Similarly, priests in the diocese of Cienfuegos now teach weekly classes on civil rights. "Our purpose is never to subvert the socialist order, but merely to enable people to become more engaged with the society in which they live," said a church official.