Pope John Paul II has directed U.S. Roman Catholic bishops to oversee what he termed the "renewal" of nuns and members of male religious orders according to strict guidelines calling for a return to wearing "religious garb" and living communally and encouraging a return to traditional occupations.

In a letter dated Easter Sunday, April 3, and released yesterday, the pope signaled an end to nearly 20 years of experimentation for religious orders of women since the Second Vatican Council.

During that time, many nuns have forsaken parochial school classrooms and hospitals for various ministries, most on behalf of the poor. That frequently put them at odds with established secular and religious authorities.

The pope appointed a committee of three of the most progressive U.S. bishops, headed by Archbishop John R. Quinn of San Francisco, to assist in overseeing the "renewal" of the religious communities within U.S. dioceses.

Quinn said the change is not a crackdown. "There is nothing in any of this that indicates that something is pervasively wrong with religious life in the United States," he said. "The pope is not calling for an investigation of religious life in the United States."

He said the pope's message is "a profound call to the bishops to encourage and strengthen religious life in its own authentic renewal."

In his letter, the pope directed the bishops to explore causes of massive defections from religious life in the last two decades and of the decline in numbers of young persons seeking to enter religious orders.

Quinn said the number of U.S. nuns has decreased from 181,421 to 121,370 since 1966. In his letter, the pope said that decline and the lack of newcomers mean "many religious are overburdened, with a consequent risk to their health and spiritual vitality." He said the situation "is a matter of grave concern to me."

At the direction of Pope Paul VI in 1966, nuns began systematic studies of their orders, their lives and work. The process of change, which coincided with the massive upheaval in the church brought about by the Second Vatican Council, led thousands of women and men to leave religious orders.

Many who remained were energized not only by changes within the church but also by exposure to secular issues such as the civil-rights struggle, protests against the Vietnam war, problems of the poor and quests for sexual equality.

Many nuns exchanged the religious garb for conventional clothing and moved into apartments in rundown neighborhoods to identify more closely with those they served.

The pope's letter, written in the florid style of similar papal missives, offered no specific criticisms of members of U.S. religious orders. But it was accompanied by a 38-page document, approved by the pope, spelling out "characteristics" and "fundamental norms" of religious life.

These guidelines, covering most aspects of life within a religious order, emphasized repeatedly that nuns and other members of religious orders should live a communal life in a religious house and "should not live alone without serious reason . . . ."

Members of religious orders "should wear the religious garb" of their order "as a sign of consecration and a witness of poverty," the guidelines said.

Fulfilling traditional religious vows of poverty, chastity and obedience "inspires a way of living which has a social impact," the guidelines said, adding that such a "witness to values which challenge society" is commendable.

The document warns members of religious orders against trying to do too many things at once. It also cautions against what it called the "temptation" to abandon work that religious orders were founded to do in favor of tasks "which seem more immediately relevant to social needs."

Quinn, who is to be assisted by Archbishop Thomas C. Kelly of Louisville and Bishop Raymond W. Lessard of Savannah, Ga., has named seven men and women members of religious orders to assist in the evaluation of U.S. religious life.

He promised that members of U.S. religious orders "will have the opportunity to present their findings in a totally American context."