Associate Dean for Undergraduate Education Lawrence Buell distributed a letter to professors this month alerting them to pronounced grade inflation in Harvard classes, faculty members said.

The letter said grades in the natural sciences, social sciences and humanities have all risen since the 1960s, but made clear that increases in the humanities have been the most pronounced, Assistant Dean for Undergraduate Education Jeffrey Wolcowitz said yesterday.

Although letters discussing grade inflation are often sent during the fall exam period, Wolcowitz said this letter was "more pointed and strong" than those of years past.

Buell was out of town and could not be reached for comment yesterday.

Thomson Professor of Government Harvey C. Mansfield Jr. said Buell's letter is the first "call to change the norm" he has received.

But despite the "call" Mansfield and other professors interviewed yesterday were less sure if the letter will have a long term effect on grading policy.

Instructor in the Department of Romance Languages and Literatures William D. Cole, who wrote an article on grade inflation in The Chronicle of Higher Education this month, said that when a dean has sent out strong letters in the past, professors seem to take notice of it. He predicted that inflation will subside for a few years, but will rise again.

Mansfield said that grades will only fall if professors act simultaneously to lower grades.

"I think it's terrible, the situation we've let arise," said Mansfield. "The problem is grader sovereignty....The administration cannot tell professors how to grade students."

Mansfield, who is often referred to by his nickname "C Minus," said that students under the pressure of getting good grades may be driven away from strictly-graded classes.

Because many classes and professors compete for students, most instructors are reluctant to give radically different grades than their colleagues are awarding.

"As long as students are getting As and Bs [in competing classes,] it is difficultto give a C," Mansfield said.

In addition, the inconsistency of gradeinflation between sciences and humanities mayinappropriately influence students' choice offield, Cole said. He said some students may decideto study the humanities because they are likely toreceive better grades than in a natural sciencefield.

The reason the non-natural scienceconcentrations experience higher grade inflationis inherent in the nature of the work, saidProfessor of Government Mark A. Peterson.

"The natural sciences deal with much morequantitative kinds of work," said Peterson. "[Inhumanities and social sciences] so much isempirical. There is so much room for ambiguity andinterpretation."

Professor of English Robert S. Brustein saidthe difference between the natural sciences andthe humanities is that in the humanities "one isforced to deal with the imagination."