Presidents of major American universities and other leaders in academia today expressed their disappointment at President Derek C. Bok's decision to step down, while praising his long and distinguished career.

"Derek Bok is surely one of the most admirable academic leaders of his time," said Benno C. Schmidt, president of Yale University. "His thoughts and balanced defense of academic values, his accounts of what is right about higher education and what needs fresh thinking, and his calm and strong stewardship at Harvard have won him the respect of his colleagues across the country."

And Robert Atwell, president of the American Council on Education described Bok as a "giant among giants," adding that his resignation is an "incalculable loss to higher education nationally."

Bok, widely considered a leader in American higher education, has been a vocal advocate of the social responsibilities of universities during his 19 years as Harvard's top administrator. Brown University President Vartan Gregorian said Bok had led the call for colleges to rebuild the nation's public education system. "He has been a great leader and very often has articulated the collective aspirations of American academies," Gregorian said.

"This is a man who for 20 years has been taking the lead on a variety of issues on every conceivable topic," Atwell said.

Gregorian said he believes Bok will speak out on social and educational concerns more forcefully once he is no longer bound by his high-profile position. "He may be able without any restraint to speak with much more forcefulness on these issues," Gregorian said.

Although Gregorian said he was surprised by the announcement, he added that he understands Bok's deci- sion to resign from a very difficult job."Being a college president now is the toughestposition in America," Gregorian said."Universities have become small city-states."

University presidents who know Bok personallysaid they will miss the friendly advice he hasprovided them over the years.

Donald Kennedy '52, president of StanfordUniversity and a member of the Board of Overseerswhen Bok was appointed, said the outgoingpresident "gave Harvard and the rest of us morethan we were owed."

"Bok is the kind of person I think of to callfirst when I need to talk over a difficultproblem," Kennedy said.

"I have the highest regard, admiration andaffection for President Bok," Gregorian said. "Iwill miss his wit and charm and intellect."

Schmidt also added that Bok has been "veryhelpful" to him.

But even those academics who are familiar withHarvard said they could offer no guesses as toBok's successor.

"Not even a fortune teller can tell us that,"Gregorian said of predicting a possible Boksuccessor.

But Kennedy said Harvard can and should pickthe next president from within its own ranks. "Mysense of it is that Harvard has an extremely richarray of talent," Kennedy said.

"I believe that they would look hard inside andthey would find the person they want inside,"Kennedy said