A well-dressed businessman wandered curiously into the brightly lit, one-room shop in Bethesda with two associates and asked, "Would you be kind enough to tell us what you do here?"

Moments later, a young woman attracted by the tropical beach travel posters sho could see from the sidewalk entered to inquire, "Is this a travel agency, or what?"

"Happens all day long," remarked Susan Boley, the clerk. "People come by and look inside and laugh."

What people are looking at is the PMA Sun Tanning Center at 7502 Old Georgetown Rd., a converted newsstand that sells the look of endless summer. For $48, a customer gets 20 coupons entitling her or him to stand inside a tiny tanning booth where ultraviolet light from fluorescent tubes can do to the skin in minutes what it would take the sun hours to do.

A bamboo-covered beach hut houses the center's two tanning booths and dressing rooms. The booths, each about the size of a telephone booth, are lined from floor to ceiling with a mirror-like plastic that reflects tanning rays originating from floor-to-ceiling fluorescent tubes positioned vertically in each corner.

The customer, usually dressed in a bathing suit or less but required to wear protective goggles stands inside the booth and turns slowly to ensure an even tan. Center employes set a timer that limits each session to between two and ten minutes, depending on the customer's complexion and ability to tan. The bulbs, unlike the sun, throw off no heat but can cause severe burns.

Maria Maroshek, the deeply tanned manager and co-owner of the tanning center, said she and her husband, a Bethesda dentist, had a friend in Europe who used such a center and "said it was terrific."

"My husband and I both like to travel and like the sun a lot," she said. "We saw a newspaper advertisement (for a tanning center), and because it was so unusual we decided to try opening one here."

Maroshek said that since the center opened Oct. 16 about 40 people have signed up for initial $48 memberships. The for-profit business also offers a one-year membership with unlimited tanning sessions for $100.

Roger Schneider of the U.S. Food and Drug Administration's bureau of radiological health said the artificial tanning centers originated in Arkansas and Tennessee and now number more than 200 in the United States.

"This is the first one I've heard of in the Northeast," Schneider said.

He added the federal agency is keeping an eye on the centers because prolonged use of ultra violet lamps may constitute a health hazard. Although Schneider said the centers are "safer than staying out a long time in the sun because there is some rational control involved," some medical authorities disagree.

Dr. Sanders H. Berk, a member of the American Board of Dermatology, said the tanning process is "like taking poison."

"It's like people who lay out on the beach," he said. "it clearly damages the skin over prolonged use. Not only sunburn, but chronic effects, like wrinkling of the skin and skin cancers."

The FDA this month ordered sunlamp manufactures to include warning labels, goggles and timers with their products to protect users from sunburn or other injury.

Beginning next May, sunlamp manufacturers and tanning centers will be required to warn consumers that the lamps give off ultraviolet radiation and that "overexposure can cause eye injury and sunburn; repeated exposure may cause premature aging of the skin and skin cancer."

Despite the known adverse effects of the sun's ultraviolet rays, the love many Americans have for the bronze body continues, and Maroshek's tanning center appears to be benefiting from it.

One of the center's first customers, 18-year-old Karen Peterson, predicted the new operation will prove to be energy efficient.

"This will cut back on trips to the beach next summer," she said, "and it will save gas."