When preparing for interviews with top colleges, applicants often rely on typed-out talking points and new suits to make good impressions. An Upper East Side private school, Spence, even offers a senior seminar during which a teacher conducts mock interviews.

Such preparations are not quite worth the trouble, current and former admissions officers said. It would be a rare interview faux pas that could disqualify an applicant, such as wearing a bathing suit to the interview, saying the school is only a fallback option, displaying bigotry, or admitting to patricidal fantasies, the admissions officers said. Catastrophes aside, they said, an interview bears little or no say in the race for top-college acceptance.

“I don’t know, quite honestly, how much it is valued in the Ivy League,” a college consultant in Ithaca, N.Y., who has worked at a top admissions office, Lucia Tyler, said. “I don’t think so, for most. I don’t think it’s valued as much.”

No Ivy League university requires an interview, and most encourage talking with an alumnus rather than an actual admissions officer — an opportunity a growing number of selective schools do not even offer. Brown canceled on-campus interviews in 2003, joining the Massachusetts Institute of Technology, which dropped them about three years before, as well as Princeton and Columbia universities. Cornell University’s College of Arts and Sciences has not only canceled on-campus interviews, it has stopped offering anything called an “interview.” What used to be alumni interviews are now called “meetings.” A spokesman for Cornell, Simeon Moss, said about half of applicants are contacted for such meetings.

In a 2005 survey by the National Association for College Admission Counseling, nearly two-thirds of colleges said they give the interview little or no consideration. Thirty-three percent said an interview bears no importance at all, up from 30% the year before.

Experts said the decline in importance of the interview is due to a surge of college applications even as admissions staffing levels have been constant. At the University of Pennsylvania, admissions officers formerly conducted their own interviews, the admissions dean, Willis Stetson, said. But as the office saw a surge of applications in the last 15 years — it now receives more than 20,000 each year — the university had no choice but to turn to an army of 7,000 alumni stationed on every continent for help, Mr. Stetson, said.

“The volume is just too great, the demand is just too bad,” a former admissions dean at Franklin & Marshall College in Pennsylvania, Peter Van Buskirk, said. Franklin & Marshall recently abandoned Mr. Van Buskirk’s practice of interviewing applicants only on campus. “I felt pretty strongly that an interview for admission needed to be more evaluative in nature,” he said. “It was not fair to have alumni make critical assessments of young people based on an across-the-table session.”

Alumni, he said, have less perspective on students, and their reports can be variable.

In Manhattan, last year’s high school seniors said they met their interviewers most often at their office buildings or a Starbucks. Occasionally, an alumnus will invite a student up to an apartment.

A University of Pennsylvania interviewer in northern New Jersey, Maria Ho, said she usually gives positive reviews — and then sees the students rejected. Recently, she said, as more and more applicants file in, even her rare bad reviews have made no difference.

“I interviewed this kid, and he actually sat in front of me and told me that Penn was his second choice and his first-place was Princeton,” she said. “There have been instances where I’ve written something as blatant as that, and the kid still got accepted. You never know.”

Ms. Ho, who has been interviewing students for 25 years and now coordinates all alumni interviews in her area, said she is still enthusiastic about the process. Even if the admissions officers don’t listen to her advice, the applicant might. “When April comes and they’re sitting with five decisions in front of them, five schools in front of them, now the roles are reversed,” she said. “We want them to think back to their Penn interview as a great experience.”

She said talking about her own college days always makes for fun nostalgia.

A private adviser to applicants in New York City and elsewhere, Steven Goodman, said relationships like Ms. Ho’s are why interviews persist, even as they are taken less seriously. “Because why would you endow a lecture series if you had no connection to the university whatsoever?” he said.

Mr. Goodman said another purpose is to discover advantages not mentioned in a high school transcript. Overhearing a parent complain about the school’s price tag, he said, would be something to write in a report. “Conversely,” he said, “what happens if all of a sudden somebody mentions something about their older brother went to the University of X and we’ve been so involved, and then we decided to endow a lecture series about such-and-such topic? A good alumni interviewer would pick up on that and would communicate that back to the admissions office.”

Harvard’s director of undergraduate admissions, Marlyn McGrath, said interviews’ role in her decision process is important, if subtle. “It’s a different kind of angle on a candidate, but it usually confirms the yes-or-no decision that we’re making,” she said. If the first interview doesn’t fill the bill, she said, Harvard will ask an applicant for a follow-up. She said the college asks for as many as 100 follow-ups in a year.

A recent graduate of Spence on the Upper East Side, Kathryn Arffa, was skeptical about alumni interviews’ importance after attending several last year. During her Harvard interview, she said, the alumnus, a young mother, spent the hour quizzing Miss Arffa on the reputations of uptown private schools. She also asked several questions about Miss Arfa’s townhouse.

Some colleges are trying to buck the trend. The University of Denver has made interviews mandatory. Although MIT stopped its own mandatory policy about seven years ago, the school has kept its alumni interviews rigorous, grading interviewers’ reports for quality and then firing those who don’t improve, the school’s interim director of admissions, Stuart Schmill, said. Mr. Schmill said the reports are taken seriously and usually give a big boost; nearly 90% of admitted students were interviewed last year, compared to about two-thirds of the entire applicant pool.

Showing up at interviews is important even for colleges that take the interviews less seriously, Jeannie Borin, the president of an educational consulting firm, College Connections, said. Just like people, Ms. Borin explained, colleges like to accept those who seem likely to accept them.