VATICAN CITY, OCT. 1 -- With a solemn mass in St. Peter's Basilica, Pope John Paul II today opened a month-long synod of bishops that is to explore the sensitive issue of the role of Roman Catholic lay people in the workings of their church.

"Gathered in the synod of bishops, we begin today, Oct. 1, our common task," the pope told the 232 prelates. "Our work is dedicated to this theme: the laity in the church, their life and their mission, for the salvation of the world."

"We nourish a profound esteem," he said, "for our lay brothers and sisters."

The bishops, selected by national conferences around the world and in part by the pope himself, are to spend October debating what specific areas and activities lay men and women should be involved in and what the limits of their roles should be in a church that traditionally has been run by an ordained male hierarchy.

It is an issue that has caused ferment in the Catholic Church since the Second Vatican Council in 1963-65 proposed giving the church's faithful, the "people of God," greater responsibility, which many in the Vatican hierarchy argue could water down the authority of the bishops and the ordained clergy.

The prospect of a greater role for the laity has given birth to such controversial experiments as the "base communities" organized in Latin America, an area critically short of priests, to take over many of the functions of the clergy. In the United States it has brought to the fore demands by women for greater equality in the church, including the right to join the priesthood.

As in previous synods held since pope Paul VI began formal papal consulation with the bishops in 1967, this synod's conclusions and recommendations will be nonbinding.

Because the current synod has been four years in preparation, few surprises are expected. The issues surrounding expansion of the role of the laity have been extensively debated in public and John Paul, as recently as last month during his U.S. tour, clearly stated his views on the subject.

In a meeting in San Francisco with selected laity from across America, he reiterated that the laity should be the church's instruments in the temporal, not religious, world. "It is within the everyday world that you the laity must bear witness to God's kingdom." he said. "It is for you as lay people to direct all temporal affairs to the praise of the creator and the redeemer."

That, the pope made clear, should start with the family, then society. He made no mention of the demands of lay people in many parts of the world -- the industrialized West as well as many poor countries of the Third World -- for more say and participation in the institutional church. The pope has rejected ordaining women as priests.

The main debate will be carried out by the 232 bishops who form the synod. Each will have the right to speak for eight minutes during the general sessions, before the synod is broken down into committees.

The church's lay people are represented by 60 "auditors" -- 26 women and 32 men -- who will have the right to speak out in some sessions but will have no vote.

In the final weeks, the bishops are expected to formulate a summary of their discussions and conclusions to give the pope.

Earlier today, the pope met with 88-year-old Cardinal Frantisek Tomasek of Czechoslovakia to discuss the restrictions placed on the church in that country by its communist rulers.

Criticizing Prague's decision to allow only Tomasek, among the country's five bishops, to come here, the pope said, "The absence of these bishops offers an eloquent indication of the conditions in which the church lives in your region."