A papal edict that caused an upheaval in Roman Catholicism was commemorated recently, as American bishops saluted it for "prophetic wisdom," but recognized obstacles to it.

The occasion was the 20th anniversary of the late Pope Paul VI's 1968 encyclical "Humanae Vitae," "Of Human Life," which reaffirmed the church's ban on contraception, and set off a church storm.Repercussions still linger in the widescale Catholic rejection of the particular prohibition and, as seen by some scholars, in the spread of dissent to other areas of church teaching.

In this country and elsewhere, the event catalyzed a searching examination of Catholic rights of conscience, and debate over it still goes on.

The encyclical, asserting an inseparable link between the unifying and reproductive dimensions of sexual intercourse, said it always "must remain open to the transmission of life."

Despite continuing resistance to the rule, bishops and some Catholic groups paid tribute to it. Also, a new study gave a positive assessment of the church's only approved way of limiting pregnancies - natural family planning.

This involves charting the wife's period of fertility and avoiding intercourse during it. In responses from 3,763 couples using the method, 70 percent found it satisfactory.

"The results verify that couples who are properly instructed and well-disposed find natural methods satisfactory and effective," said Chicago's Cardinal Joseph Bernardin, head of the bishops' pro-life committee.

It was the first such nationwide study of its kind, with answers to questionnaires gathered from couples instructed in the use of natural methods in 24 diocesan programs across the country.

The study, funded by the Knights of Columbus, a national Catholic fraternal organization, found that two-thirds of the husbands and wives consider it important to be "in conformity with church teaching" in their sex lives.

Only about 10 percent reported unintended pregnancies in the past year.

"The results are highly encouraging," said Auxiliary Bishop James T. McHugh of Newark, N.J., director of the church's Diocesan Development Program for Natural Family Planning.

However, as indicated by numerous surveys over the past decade, large majorities of Catholics, generally found at more than 70 percent and ranging up to 90 percent, disagree with the church's ban on contraception.

That situation, multiplying into dissent on other church fronts, burst widely after the promulgation on July 29, 1968, of "Humanae Vitae."

It generated public dissent from about 650 American Catholic theologians, including most of some faculties, and created prolonged turmoil in Washington between priests and the late Cardinal Patrick O'Boyle.

Several national hierarchies - in Canada, Belgium, Austria, West Germany and elsewhere - affirmed conscientious decisions about the issue - similar to a 1971 Vatican compromise settling the dispute in Washington.

Meanwhile, in the early phases of the outcry, U.S. Catholic bishops in 1968 issued a statement recognizing rights of responsible theological dissent.

But in 1986 this was repudiated as "unworkable" by Washington's Archbishop James Hickey, now cardinal-designate, after the Vatican barred the Rev. Charles Curran, a noted moral theologian, from teaching theology.

He dissented from various church sexual teachings, including bans on contraception and divorce.

Paul VI's controversial encyclical came in the wake of the 1962-65 Second Vatican Council, from which he had removed the issue. To study it, he set up a broad commission of scientific and religious scholars.

Its strong majority recommended dropping the contraception ban, and Paul's reassertion of it hit like a thunderclap.

He attributed resulting difficulties largely to "a certain climate of expectation which had given rise, among Catholics and in the wider circle of public opinion, to the idea of presumed concessions..."

Twenty years later, the U.S. bishops' Committee for Pro-Life Activities said "we see ever more clearly the prophetic wisdom" of the church's position and "the courage of Pope Paul VI in reaffirming" it.

At the time he did so, they said, the birth-control pill was relatively new and people "were still reeling from the `sexual revolution' of the 1960's... Today's climate is different again.

"Looking back over the past 20 years ..., we can see a gradual decline in family size and an increase in divorce, both notably pronounced among Catholics, and an overwhelming assault on the sacredness of human life in judicial decisions and social policies regarding abortion.

"We find in our society a growing ambivalence regarding children, and an increasing tendency to equate the bond of marriage with mere cohabitation."

Against these tendencies, the bishops said, adherence to the church's teaching against contraception helps married couples develop sensitivities to each other's needs that "solidify the marriage relationship.

"Efforts to live their sexuality in accord with the teaching of the church brings to married couples peace of mind and conscience. It also deepens their faith and affirms their reliance on God's providential care."