Mary Brewster, 59, a data processor with the Navy Federal Credit Union in Vienna, knows a good deal when she sees it. Last Saturday she paid only $8 for a complete physical examination at a health fair in Arlington where volunteer medical students, nurses, doctors and American Red Cross workers tested Brewster's hearing, blood, vision, mouth, neck, skin and physical fitness.

Brewster was one of 267 people, a 12 percent increase over last year, to receive a health screening at Thomas Jefferson Junior High School, which inaugurated Virginia's seventh National Health Fair Week. Sponsored by Chevron, WTTG (Channel 5), WASH radio and the National Health Screening Council for Volunteer Organizations Inc. (NHSCVO), a private nonprofit organization based in Bethesda, the health fairs end Sunday.

Founded in 1975, NHSCVO, Inc., has offered health screening and educational services to more than one million Americans. This year, there are 70 cities in 20 states providing health fairs and, altogether, they will offer health care services worth $270 million.

During health fair week this week, an estimated 8,000 adult Virginians--they must be at least 18 years old--will head to Virginia malls, schools and recreation centers for free checkups at 12 health fairs. Examiners at each site will offer tests for anemia, vision and blood pressure, plus counseling and referral services. Some sites have podiatry, sickle cell and breast exams and oral screening for cancer, as well.

Brewster's experience was typical. Her first examination concerned her height and weight.

"My daughter says I'm on a 'see' food diet," said the five-foot-six-inch Brewster with a laugh. "I see food and want to eat it. I'm just too short for my weight. I have the perfect weight 208 pounds for someone 8 feet tall." She said her weight is high in part because she is recovering from an ankle operation.

The hearing test was next, and Brewster was skeptical about the outcome. "After listening to the loud music my two children played as teen-agers," she said, "I'm likely to have poor results."

Then, in short order, a nurse informed Brewster her blood pressure was a little high; she took a blood chemistry test for $8 that normally costs $50 in a doctor's office; discovered that she is not anemic when some of her blood sank to the bottom of a copper sulphate solution, and was told by an Arlington ophthalmologist that the pressure inside her eyes was "quite fine," thereby ruling out glaucoma.

Next, while waiting for the pap, dental and skin tests, Brewster watched two 10-minute films produced by the American Cancer Society ("How to Examine Your Breasts" and "The Cancer No One Talks About," i.e., rectal cancer).

The low point was when Brewster fell during the three-minute cardiovascular fitness test. Shortly after, and very pale, she sat down before the test's completion to recuperate.

"Yours is not a valid test," she was told by the examiner. "I recommend exercise, probably walking. I also recommmend your visiting a cardiologist for a treadmill test."

After a yoga lesson "to make more efficient a normal function, breathing," and a neck massage, Brewster was finished.

Brewster enjoyed her massage, given by a therapist from the massage therapy center of Northern Virginia, most of all.

"I'd like one of these each evening at bedtime," she said. "I've now got happy shoulders. Can't you see they're grinning?"

For times and locations of health fairs in Northern Virginia this week, see calendar listings in This Week on Page 13 of The Weekly.