(FORTUNE Magazine) – Bruce Wong was a recruiter's worst nightmare. He liked his job as a clinical scientist at SmithKlein Beecham and had no desire to leave. Wong had agreed to interview at archrival Bristol-Myers Squibb only because he was friendly with the headhunter. But one interview turned into a dozen, and the process dragged on for months. So the headhunter was a little nervous about presenting Wong with his client's latest requirement.

"There's this outside consultant they'd like you to meet," the recruiter, Kevin McGrath, remembers stammering.

"What do they want?" Wong joked. "To send me to a shrink?"

McGrath was silent. The answer was, well, yes.

Bristol-Myers is among a growing number of FORTUNE 500 companies that are adding one more hurdle to the executive hiring process: a psychologist. Rank-and-file employees have been subjected to "personality tests" for years; now it's management's turn. Dell Computer, General Electric, Motorola, and others have recently started requiring candidates for top jobs to undergo lengthy interviews with outside psychologists, take paper-and-pencil tests, or both.

Companies go to all this trouble and expense--the current rate for an evaluation is about $5,000--because they fear that despite the candidate's stellar credentials, obvious talent, and glowing references, he just won't fit in. And that can be a company's undoing. "A poor job match is not only harmful to the individual but also to the company," says management consultant Ram Charan (co-author of "Managing for the Slowdown," in this issue).

Indeed, "fit" is becoming the rallying cry of recruitment and retention experts across corporate America. Two new books, Now, Discover Your Strengths and Executive Instinct, push the concept, arguing that people really can't be rewired. Either you're a leader or you're not. Either you have empathy for others or you don't. In Strengths, Gallup consultant Marcus Buckingham estimates that 80% of workers don't truly fit their jobs because they aren't using their innate strengths. John Kelly, CEO of Alaska Airlines and a big advocate of psychological testing, agrees. "You can't help how you are born," he says.

By that logic, the onus is on the person doing the hiring to get it exactly right. Accenture's Paul Taffinder figures that in a traditional interview managers typically decide on a candidate in the first two minutes and spend the rest of the interview convincing themselves that this snap judgment is correct. Kevin Murphy, former head of the Society for Industrial and Organizational Psychologists, estimates that such interviews are only 65% accurate in judging an applicant's potential strengths and leadership style. Adding testing or other psychological tools can raise accuracy to 85%. Says industrial psychologist Richard Hagberg: "We measure 'automatic-pilot mode,' how people will behave when they don't pay attention." He says this gives a better picture of the way a candidate is likely to act on the job, when not trying to impress an interviewer.

During its CEO hunt, Hewlett-Packard put Carly Fiorina and other finalists through a two-hour, 900-question personality test that Hagberg helped develop. The candidates were given statements like "When I bump into a piece of furniture, I don't usually get angry," and asked whether they were true or false. Fiorina must not mind a few bruises. Hapberg wouldn't disclose her answers but says the overall results of the test indicated that Fiorina sees the "big picture" and "gives messages that inspire."

At Bristol-Myers the tests started as a way to boost retention rates. Three years ago managers began noticing that executives hired from the outside weren't as successful as those promoted from within. The outsiders tended to leave, voluntarily or not, often after just a year. Says Ben Dowell, who runs Bristol-Myers' Center for Leadership Development and who studied the departures extensively: "What came through was, those who left were uncomfortable in our culture or violated some core area of our value system."

To define its culture, Bristol-Myers hired RHR International psychologist Dante Capitano. After interviewing senior managers for four months, he concluded that Bristol-Myers is a team-driven organization, true to its R&D roots. It nurtures self-motivated and intellectually curious people who are concerned with the greater good.

Which brings us back to our job candidate, Bruce Wong. During his session with Capitano, Wong was asked where he did his postgraduate work. His answer--at Canada's McMaster University--was important, not because McMaster is a topflight institution (it is) but rather because he had left his home in New Zealand to attend, demonstrating both natural curiosity and a willingness to go anywhere to obtain the best training. Nor did it matter that Wong was well respected in his field of "outcomes research" (the study of how medicines affect a patient's lifestyle); what mattered was that he had stumbled into the field as a way to stay close to a woman he loved. That, says Capitano, shows flexibility and work-family balance. After the session, Capitano presented his findings to the hiring committee, which concluded that Wong would be a terrific fit with Bristol-Myers. He got the job as vice president of outcomes research, and chances are he'll stay awhile. Since adding the psychological interviews, the company has seen its retention rate among outside hires climb 25%.

Not everyone is gung ho about psychological testing. Management style is impossible to quantify, critics say. Experts also disagree on whether people can fake the tests. (Does Carly in fact curse when she bumps into the damn chair for a third time?) And there's the question of whether the tests violate an applicant's privacy. Lewis Maltby, founder of the pro-labor National Work Rights Institute, notes that some tests ask about your sex life, religious beliefs, even bathroom habits. "There are questions I wouldn't even ask my wife," he scoffs.

You'd think such intensely personal questions would send job applicants running to the competition. Wouldn't a reluctant candidate like Wong be put off by a lengthy, probing interview? On the contrary, companies are discovering that some people actually like divulging their secrets to a company shrink. After all, who wouldn't be tempted by a job that is sooooo important that it requires six hours of psychological assessments? For Wong, the drawn-out selection process was precisely what persuaded him to give up his comfortable job at SmithKlein Beecham for something new at Bristol-Myers. Ditto for his new colleague, Judy Robertson. She joined Bristol-Myers last April after 15 interviews and considers her meeting with the psychologist the best time spent in her entire career. "You never want to join a company that is too quick to judge and hire," she says. Obviously, a perfect fit.

FEEDBACK: onthejob@fortunemail.com