It's something people often daydream about -- particularly during bikini season. Wouldn't it be great if some ugly bulge of fat could just be removed, sliced off, gone forever?

For an estimated 50,000 Americans, the idea is more than a fantasy. At least that many patients have had surgery to remove fat from their bodies since 1981, when the procedure known as fat suction was first introduced in the United States.

But the operation, formally called suction-assisted lipectomy or lipolysis, is not the answer for most daydreamers says Dr. Gregory Hetter, a Las Vegas plastic surgeon who heads the Lipolysis Association of North America. He turns down two of three patients who seek the operation, either because they have unrealistic expectations or because they would do better seeing a diet specialist.

"This is not a substitute for dieting or a procedure for obese people," Hetter said. "People I do operate on are close to their approximate recommended weight, but have a disharmonious figure that doesn't respond to diet or exercise."

Fat suction involves tunneling a straw-shaped instrument with a rounded blunt tip into a smaller than half-inch incision near unwanted fat deposits. A vacuum apparatus sucks the fat out.

The deposits are gone forever. Fat cells in adults don't regenerate; they only grow larger or smaller, depending on calorie intake.

Lipolysis can be applied virtually anywhere there is excess fat: on the face, neck, stomach, upper arms, thighs, hips or buttocks.

Doctor and hospital fees run from $1,200 to $1,800 for removing fat from under the chin, $2,500 to $4,000 for troublesome "saddlebag" hip areas and $2,000 to $3,000 for heavy calves and arms, according to Hetter. So far, the costs are not covered by most insurance policies.

The procedure does not leave large scars, Hetter said. Most patients can be back at work in about a week.

Statistics he compiled with fellow surgeon Frank Herhahn of Albuquerque show that 87 percent of their patients said that they were satisfied with the results; 95 percent said they would go through the procedure again. Eighty-five percent said they felt better about themselves after the lipectomy.

The amount of fat removed varies widely, according to a patient fact sheet from the office of Dr. Lawrence Reed, a plastic surgeon from Beth Israel Medical Center in New York. As little as one to two ounces can be removed from the ankle, between 8 and 10 ounces from a small abdomen and up to 14 to 21 ounces from the thighs in patients with "riding-britches" deformity. The total amount of fat removed can reach four to six pounds or more when multiple areas are treated.

The best candidates for lipolysis, plastic surgeons say, are those who are under 40 with good skin tone, so the skin will contract naturally. But the procedure has been done on patients as old as 75 who have acceptable skin tone or were willing to accept a less-than-perfect result for a smaller pant size or loss of a few inches of fat.

Hetter said patients who want instant gratification are frequently disappointed. Improvements begin to show up after three weeks, when swelling begins to decrease, and it takes three months or longer before total improvements are noticeable.

"It was traumatic," said Jordana Ayres, 32, a part-time student and part-time manicurist from Las Vegas, who had two pounds of fat removed from her thighs. "After the surgery, I was larger because of the swelling. It took three months until I started to notice the results and six months until I was really happy with what had been done."

The complication rate for lipolysis is estimated at less than 2 percent, Hetter said.

The most common problems reported after lipolysis are abnormal lumps, bumps or washboard appearance of the skin that results from removing too much fat. Skin also may change in color when there is significant bleeding. Permanent discoloration can occur, but that is rare.

Pain is another common complication, says a report from the American Society of Plastic and Reconstructive Surgeons. Most pain isn't long-lasting, but the report notes that "some patients complain of tearing and burning sensations which last for months."

Life-threatening complications also are possible, but rare, says Dr. Frederick Grazer, president of the American Society for Aesthetic Plastic Surgery. He is aware of about a half dozen deaths associated with fat suction operations, but said the patients were undergoing other surgical procedures at the same time and died after blood clots traveled to their lungs.

Meanwhile, a committee chaired by Dr. Eugene Courtiss, chief of plastic surgery at the Newton-Wellesley Hospital in Newton-Lower Falls, Mass., is conducting a study for the Food and Drug Administration to affirm that the equipment used in the surgery is safe and effective for fat removal.

The same equipment is already being used for abortions. Courtiss said there is no indication the devices are not safe for fat suction procedures, but that current safety records are based on reviewing large numbers of cases after the procedure was performed. FDA approval requires that 200 patients be studied before, during and after surgery. Results will be reported in about a year.

Fat suction is difficult because plastic surgeons must "evaluate how a patient looks today and also how the person will look years from now," Grazer said. "We have to extrapolate what will happen if we take out too much fat and the patient begins to lose weight with age."

He anticipates that some patients may develop washboard appearances as time passes, but said he doesn't expect this to be a major problem.

Some plastic surgeons are taking the fat suction process beyond cosmetic operations. Dr. Luis Vasconez, head of plastic surgery at the University of California at San Francisco, has used it to reduce fatty back tumors, to contour skin flaps that will be transferred to fill body deformities, to get a better appearance for breast reductions and, in limited cases, to reduce abnormal swelling in the body, called lymphedema.

"Fat aspiration has allowed me to approach problems with a safer procedure that doesn't require such a large operation," he said.

"Once we learn more about the procedure, I think there will be more potential for treating obese patients," said Grazer. He predicted that one day doctors may be able to detect persons who are destined to be obese and selectively suction some fat while they are young.

Attempts to remove excess fat are not new. French references to fat-removing surgery date back to the early 1920s. One of the earliest efforts to surgically remove fat deposits from a dancer's knees led to injury of a major vessel, amputation and the first lawsuit over esthetic surgery in France.

In the 1970s, interest resumed and three European plastic surgeons independently reported their techniques for removing fat. Two Italian plastic surgeons are credited with adding the first suction equipment to the procedure.

A French plastic surgeon, Dr. Yves-Gerard Illouz, designed a rounded, blunt-shaped tube that eliminated previous problems caused by use of sharp instruments. By 1980 he had used the technique successfully on 300 patients.

The first fat suction operation in the United States was performed in March 1981 by Dr. Norman Martin, a Los Angeles ear, nose and throat surgeon.

In 1983 a committee of the American Society for Plastic and Reconstructive Surgery traveled to France to review the procedure and reported that suction lipectomy "is safe and effective in trained and experienced hands and offers benefits which heretofore have been unavailable."

Physicians differ over what constitutes "trained and experienced hands," with plastic surgeons arguing that the operation should be performed only by board-certified plastic surgeons, and others disagreeing.

Said Martin, who has performed 3,000 fat suction operations since 1981, "I think it should be done by doctors who know it best, who have the best track record and who have the most experience doing it."