Joan Voight was a three-pack-a-day smoker. She gave up going to the movies because she couldn't make it through the feature without a cigarette.

Then the 30-year-old World Bank research assistant -- who had tried everything else to quit smoking -- went to a free, two-hour group-hypnosis session. That was in 1974. She hasn't picked up a cigarette since.

Voight is one of increasing numbers of Americans undergoing hypnosis for self-improvement, or for treatment of a wide variety of medical, dental and psychological problems.From its exotic beginnings at the dawn of human history to its sometimes hocus-pocus Hollywood image of today, it has become almost commonplace.

Hypnosis has been sought and used, for example, by:

A payroll accountant who says she lost 30 pounds through a hypnosis weight-reduction clinic after "everything else failed."

An amateur soprano who sought relaxation in hypnosis so she could hit the high notes in an opera production.

Amateur and professional athletes trying to increase their concentration and motivation. Bethesda hypnosist Gary Hayman says his clients include pro-golfers, tennis players, skiers and a female member of the Olympic swimming team.

Washingtonians unnerved by riding those deep escalators at Metro's Rosslyn and Dupont Circle stops.

Lieutenant colonels, facing their first Pentagon briefing, who rehearse the presentation under hypnosis.

Dental patients, allergic to Novocain or afraid of the needle, who seek painless treatment without the shot.

Mothers wanting to go through painless natural childbirth. "The mother is completely awake and alert during the birth. The process is awesome," says clinical psychologist Melvin A. Gravitz.

"We can use hypnosis as an anesthesia for major surgery -- amputations and open abdominal and brain surgery."

Policemen, to help witnesses recall crime details they think they have forgotten. In the famous Chowchilla school bus hijacking, officials got a lead on the culprits when the hypnotized bus driver remembered a crucial license plate number.

And in one unusal case, Dr. Toussaint Celestin, assistant professor of psychiatry at Howard University, is helping a young marketing consultant dig back into his memory to recall a night two years ago when he suspects he was visited by a UFO -- a night that is otherwise erased from his mind. The man, a former Navy pilot, has been troubled about his inability to recall that night. f

What is hypnosis?

Gravitz defines it formally as a "verbal way of producing an altered state of awareness or consciousness." To Hayman, "It's nothing more than suggestion" -- as simple as "a mother telling her injured child she will kiss his knee and make it well."

We all may have been under a form of hypnosis at one time or another, say practitioners, while daydreaming, watching TV or listening to a stirring Sousa march.

The Hollywood image of hypnosis -- blacked-caped magician dangling a bauble and repeating "You are in my power" to a prostrate blond -- is disappearing. The American Medical Association in 1958 recognized hypnosis "as a useful technique in the treatment of certain illnesses and disorders when employed by qualified medical and dental practitioners." It is taught in medical schools. q

Health professionals trained in hypnosis emphasize they use it as one therapy among many. Though they tend to agree that hypnosis is a "benign" treatment, they also caution it is not something to be played around with, especially in treating physical and psychological problems.

"Hypnosis is a very powerful tool psychologically," says Gravitz. "It ought to be used judiciously."

These professionals express concern about possible problems if nonmedically trained hypnotists work with clients needing medical and psychological help. In the largely unregulated field of hypnosis, "Anybody can and anybody does hang out a diploma," says Gravitz.

If not medically trained, many "nonprofessionals" are nevertheless skilled hypnotists. They usually see clients seeking self-improvement: The most common goals are to lose weight or to stop smoking. Nonprofessionals sometimes work under the supervision of a doctor, dentist or psychologist, from whom they get referrals.

One lay group, the Association to Advance Ethical Hypnosis -- whose 1,500 members include both medical and nonmedical practitioners -- has set stringent standards for members, in part to help define the sometimes blurred line as to what is, or is not, a medical or psychological problem requiring a health professional.

The association, for example, wants its members to get a doctor's authorization for any client being hypnotized for weight control. "Obesity is a medical probelm," insists association director Harry Arons, although other hypnotists disagree.

How effective is hypnosis?

Phobias such as fear of flying, says Gravitz, "respond very nicely to hypnotherapy." Basically, he says, it's a matter "of unlearning a previously learned pattern and subbing a new pattern. For whatever reason, hypnotized subjects learn more effectively, more quickly and respond better."

When it comes to enhancing an athlete's motivation, he says, "I can't hypnotize you to run a mile in two minutes, but you will run fast."

Wladyslaw Michaluk, whose Hypnosis Training Center offers free, two-hour smoke-cessation clinics every Wednesday (the one Joan Voight attended), claims a 62 percent success rate based on follow-ups six months and three years afterwards. Michaluk sees it as channeling the "powerful" force of imagination "in a positive direction." Since 1968, he has worked with 12,000 at the clinics.

Damon (he uses only his first name professionally), an East Lansing, Mich., hypnotist who travels about the country hypnotizing up to 500 people at a time to stop smoking, estimates his success rate at 87 percent based on random follow-ups. He claims to have hypnotized over 600,000 people for smoke cessation and weight control since 1969. He has scheduled Capital Hilton smoke-cessation and weight-loss clinics ($35) Feb. 20.

Michaluk and Damon say you can kick the habit cold-turkey after one two-hour session, if you practice special self-hypnosis techniques faithfully for a period afterward. Others, including Arons, say you have a better chance if you taper off gradually over several sessions. Some hypnotists say group sessions work better; others that it is individual treatment.

They agree, though, that the smoker's motivation is what counts.

Joan Voight's hypnotist worked on her self-image, telling her she would "feel so much better because you'll be in control of yourself." Others use an aversion suggestion. "Your next cigarette will taste awful," a Maryland hypnotist told Diann McCormick, 37, a Washington insurance woman. It did, but not enough to get her to quit for more than 10 days.

The success rate for weight loss through hypnosis is generally lower, say practitioners. "When someone stops smoking, he sees the results immediately," says Gravitz. "It takes time to lose weight."

One thing is sure, practitioners stress: Be wary of anyone who guarantees success.

Costs vary from the free smoke-cessation clinic to $50 or more an hour for private sessions with a psychologist or lay practitioner. They may use a variety of methods to put you into hypnosis, including such old-movie gimmicks as a whirling spiral or sparkling pendant.

"We don't need them," says one hypnotist, "but the clients expect them. If it helps, we use them."

Most people can be hypnotized, say practitioners, at least to a light state that permits work on habit control. The exceptions may be persons with very low IQs and those who have major mental problems.

If you've always thought it was the weak-minded who would be the most susceptible, this may come as a surprise. As David Gouch, a doctor, and Garland H. Fross, a dentist, write in "What Every Subject Should Know about Hypnosis," the "strong-willed, more intelligent persons are usually the better subjects."