She served cocktails to gamblers in a Reno casino. And she worked 16 years in the Social Security bureaucracy to support her daughter.

Now, at the age of 51, Gail Fredericks is doing what she wants, not what she must -- becoming a doctor.

When she walks off the stage of the Meyerhoff Symphony Hall next week clutching a medical school diploma, the blond grandmother with the explosive laugh will be the oldest graduate in the 187-year history of the University of Maryland at Baltimore's medical school.

"There are doctors who retire at my age because they're burned out," Ms. Fredericks says. "I'm NOT burned out!" With her Mickey Mouse watch and wide, joyful smile, Ms. Fredericks could be a poster child for the medical profession.

She gushes about the prospect of helping people and looks forward to a late-in-life career as a family practitioner.

Not long ago, Ms. Fredericks took time to counsel a young woman who had come to the hospital emergency room. The discussion ranged from the woman's goal of going to law school to the dangers of AIDS.

"I told her, 'You're too wonderful a person to take chances with your life and that's what you're doing having unprotected sex,' " Ms. Fredericks says.

At the end of their conversation, the patient told her: "I wish you could be my doctor."

Few medical schools were willing to take a chance on Ms. Frederickswhen she applied four years ago at the age of 47.

"Some schools were saying, 'You're going to finish your residency at 55. Give us a break,' " she remembers.

"My response was, 'I'm going to practice as long as I'm competent,' " she says.

"People like me have a lot to offer. Even if we don't have the energy of a 25-year-old. We have the life experience and, hopefully, we've learned some compassion in those extra years that a 25-year-old just hasn't had the opportunity yet to acquire."

Nationally, Ms. Fredericks belongs to a select group. Of the 16,000 people entering medical school in the fall of 1992, the last year for which statistics were available, only 795 were 32 or older, according to the Association of American Medical Colleges.

The average age of new medical students was 24.7 that year, slightly higher than a decade earlier.

"Gail has a perspective on life that most medical students do not have," says Dr. Kevin S. Ferentz, one of Ms. Fredericks' professors. "Most of the important stuff [about being a doctor] you can't teach. They either come in with it, or they don't have it. Gail came in with an above-average dose and it showed."

Ms. Fredericks grew up an only child in California. Her father was a department store buyer, her mother a housewife.

In 1960, she enrolled in the theater program at Immaculate Heart College, a small women's school. After a couple of years she got married, had a baby at 20, and dropped out.

When the baby, a daughter, Wendy, was a year old, the marriage broke up and Ms. Fredericks went back to study English at Fresno State.

"I had my daughter. We didn't have any money, but it didn't matter back then," she says.

"It was that time. We were going to change the world through love. There were some social inequities that people believed needed to be corrected."

She pulled baby Wendy in a red wagon in a march on Sacramento when Ronald Reagan was governor to protest the tuition instituted at California colleges.

Ms. Fredericks went on to earn a master's degree, doing her thesis on writer Christopher Isherwood. She moved to Reno and began doctoral work in medieval English, moonlighting as a cocktail waitress at Harrah's casino.

She abandoned graduate school, though, when it became clear that it would be almost impossible to get a teaching job even if she earned a doctorate in English.

In 1974, she applied for work everywhere -- at banks, the government, libraries.

She landed at the Social Security Administration in Reno and worked for 16 years as a claims representative, field representative and later an operations supervisor.

Early on, she also had a second job as a restaurant cocktail waitress.

"I loved it," she says. "It was my job to make their evening as pleasant as it could be.

"I was very grateful for both of those jobs. They put braces on Wendy's teeth. I was able to buy a house."

As Ms. Fredericks reached her mid-30s, her mother was losing a painful fight with cancer. Ms. Fredericks was struck by the insensitivity displayed by one of her mother's doctors, who paid little attention to his patient's wishes not to be kept alive by extraordinary measures.

"I thought about the families who didn't have somebody there," she says.

"It didn't seem to me that I was making that much of a difference as a bureaucrat and [becoming a doctor] seemed to me a valid way of making a difference."

Soon after her mother's death in 1976, Ms. Fredericks made a tentative stab at medical school. The admissions people at the University of Nevada were not encouraging.

"They said, 'No, you'll never get in,' " she says.

Ms. Fredericks says she "moped" for years.

"I finally said, I'm going to try. I can't spend half of my life saying they told me, 'No.' I had just decided that one way or the other I was going to practice medicine."

In 1986, she enrolled at a Reno community college and later the University of Nevada, taking the science and math prerequisites she had skipped as an undergraduate.

She took some 16 courses over a four-year period and compiled a 4.0 grade-point average. She applied to 14 medical schools.

"I was very actively discouraged by some. I was told I would never get in, or if I got in I would never get a residency," she remembers. "A school has to feel it's investing time and money in each student it accepts. The school should ask, 'Is society going to get a fair return on its investment?' "

One day a call came from a member of the UMAB admissions committee, the appropriately named Dr. Santa Johnston.

It was good news.

"I cried. I laughed," she recalls. "I knew I would get a chance."

That year, 1990, Ms. Fredericks was one of the 2,496 people who applied to UMAB medical school, competing for about 145 places.

Dr. Mickey Foxwell, associate dean of admissions for the medical school, says his 10-member admissions committee was impressed by Ms. Fredericks' experience and attitude during interviews.

"The idea of serving society was much more on our minds. We were beginning to look for people we thought might do that," he says.

For four years, Ms. Fredericks has lived in a small apartment in downtown Baltimore, far from her daughter and grandson in Reno. Shetapped her savings to pay the $45,000 in tuition bills. She was mugged twice and the city air triggered her asthma.

And, while she has nice things to say about her classmates, most of whom are younger than her daughter, she spent a lot of time by herself.

"I'm not considered a big partyer," she says.

She went running in the Inner Harbor area and shopped at the downtown Farmer's Market on Sundays. But mostly she studied and put in the requisite long hours in the hospital.

"I needed to justify that investment so that when the next 40-something-year-old applies, that they wouldn't say: 'Look at Fredericks. We let her in. Boy, was she a dud.' "

While she did well academically, finishing in the middle of her class, Ms. Fredericks most impressed her professors with her enthusiasm and commitment to medicine.

"There are plenty of physicians who are young and give up the practice of medicine because they're unhappy with it," says Dr. Ferentz.

"At least with someone like Gail, it's so clear that this is the road she wants to take. Even if she gives medicine only 10 or 15 years, I think the investment will pay off beautifully."