When Harvard psychiatrist John E. Mack published a book last year about people who say they have been abducted by aliens, the reaction was strong and swift.

The book, entitled "Abduction: Human Encounters With Aliens," quickly became a bestseller, far outstripping sales of his earlier "Borderline States in Psychiatry" and even outselling his Pulitzer Prize-winning biography of Lawrence of Arabia.

An eminent senior psychiatrist, Mack soon found himself the country's most credible spokesman for the view that the thousands of people who say they have been kidnapped by creatures from another place or dimension are not deranged.

He did the usual author's tour and even made an appearance on Oprah Winfrey's television show. Grant money from Rockefellers and others started flowing, and he became a topic on the Internet. Thousands read his book, and hundreds thanked him for validating their experiences.

Others, however, were not so impressed. In academic circles, Mack was considered over the top -- methodologically suspect and perhaps a bit unhinged. Certainly, some felt, this was conduct unbecoming a senior, tenured professor at Harvard University. The doubters included the dean of the Harvard Medical School, Daniel C. Tosteson, who launched a secret inquiry into Mack's conduct that is soon expected to issue a recommendation. The investigation may be nearly complete, but the impact seems far from over.

The Mack affair -- both his findings about alien abductions and his treatment by the dean -- has caused a stir on the Harvard campus and sent ripples farther afield, raising questions about research methods, academic discipline and freedom of thought.

"I think this is a core, central case of academic freedom," said Harvard Law School professor Alan Dershowitz. "No matter what happens, the damage has been done. The next young scientist who is thinking about going into some field that is not mainstream will have to think twice."

Tosteson refuses to discuss the matter. "There is no general information regarding a review process relevant to this particular case or others that the school is in a position to discuss," medical school spokeswoman Karen McGinity said.

According to Mack's lawyer, Roderick MacLeish Jr., the dean appointed a three-member panel, which has met more than 25 times but never spoke to Mack until MacLeish insisted that it do so. The lawyer complained that the panel trampled on Mack's rights and followed no rules of procedure.

The committee is headed by Arnold Relman, former editor of the prestigious New England Journal of Medicine. Like Tosteson, Relman would not come to the telephone. "He has no statements to make," an aide said.

James Rowe, a vice president in Harvard's central administration, tried to explain. "Harvard has many policies that deal with faculty misconduct or discipline issues, as does the medical school. This is not a case involving misconduct or discipline," Rowe said. "What is going on is an ongoing review of Dr. Mack by senior faculty, in a peer review process, at the medical school, looking at his research methodology."

Dershowitz said the investigation amounted to a "kangaroo court" typical of academic institutions.

In an interview and in public appearances, Mack, 65, comes across as thoughtful and professional. Among some of his colleagues, however, he is seen as something of an eccentric, a man of many enthusiasms who has embraced the est movement, anti-nuclear activism and, now, aliens.

Privately, one Harvard psychiatrist complained that Mack ruined a dinner party by going on and on about his spiritual theories and his conviction that the familiar physical reality is just one of several. Others grouse that he is bringing public ridicule and scientific shame to Harvard. But Mack's many defenders say he is guilty of nothing more than becoming popular and well-funded and that his critics are just jealous.

At the American Association of University Professors, the Mack case is not being taken lightly, according to Jonathan Knight, an associate secretary who works on the organization's committee on academic freedom, tenure and professional ethics.

"One doesn't encounter this very often in American higher education," said Knight. "It is very unusual to inquire about competence arising from questions about what someone has written," although Knight added that deans occasionally need to make discreet, informal inquiries.

It is exceedingly rare for professors to be disciplined. According to reports filed with the AAUP, Knight said, there were not more than a few dozen dismissals a year among about 750,000 professors nationwide.

Usually, academic discipline is invoked for bad acts, such as plagiarism, sexual harassment or medical malpractice. What makes Mack's case so troubling, according to his supporters, is that the psychiatrist is not suspected of any bad acts -- only of bad ideas.

In a recent interview, Mack declined to discuss specifics of his case but said the investigation has been painful. "When I heard about this phenomenon in 1990, I was very doubtful. I thought it must be some kind of mental illness," he said. "I came gradually to the conclusion that I could not find any psychiatric explanation or other explanation except that some kind of trauma happened to them."

Eventually, he said, he came to believe that his responsibility was to help people with abduction stories -- known as "experiencers" -- to deal with their feelings. "I don't say, Yes you have been abducted.' I approach this with a skeptical and questioning attitude," Mack said.

Now, he said, he considers the abduction phenomenon "an authentic mystery" that merits further research. He is conducting some of that research himself, comparing 40 "experiencers" with a control group of 40 other people.

He said it was his publisher's publicist who urged him to appear on "Oprah" and "Larry King Live." "I've been criticized for it. But on the other hand, this is a matter that is important to the public at large as well as the professional community," he said. "In academic circles, one can look askance when a professor goes on a popular national television show like that." As for himself, Mack said he has never been abducted and considers the whole issue an open question. "It operates as if it were another intelligence reaching us," he said. "What the reality status of these beings is, I don't know." CAPTION: Psychiatrist John Mack wrote the best-selling book "Abduction: Human Encounters With Aliens," a project that prompted Harvard Medical School's dean to assign a panel to secretly investigate the senior professor.