IT IS A crisp, black night deep in the heart of Texas. But for 8,000 women who have trooped to Dallas from all over the U.S. and Canada, it is the most spectacular night of the year.

Several hundred pink Cadillacs are parked outside the Dallas Convention Center. Charter buses are disgorging crowds of excited women who have dressed to the nines.

It is awards night at the 17th Annual Seminar of Mary Kay Cosmetics Inc., a Dallas-based company that makes the selling of cosmetics and beauty creams a way of life.

Rena Tarbet of Fort Worth is threading her way through the crowd. She has now changed from her navy polyester Mary Kay suit into a red chiffon gown. On the arm of Eddie, her husband of 20 years, she proceeds to the front row of the mezzanine to await her moment on stage. Tonight she hopes to be named No. 3 sales director in the entire company, which last year grossed $56 million in wholesale volume.

While a bluegrass group provides a frenetic pre-show entertainment, Rena and Eddie hold hands and call out to various members of Rena's sales force. "Hi, darlin'!" she hollers to one. "This is it! Our night! Hope for No. 3!" In the year just past, Rena has directed her unit in ringing up more than $750,000 in cosmetics sales.

This night culminates 13 years of work for Rena Tarbet. Before joining Mary Kay, the only product she had ever sold was Girl Scout cookies. Today she earns an income several times that of her husband.

The Tarbets live in a treeless suburb of Fort Worth in a twice-expanded tract house with a swimming pool. They have three teen-age children. Every week the family faithfully attends the Church of Christ. They consider Rena's Mary Kay career second only to their religion and their family life. In many ways, they represent the spirit of the Mary Kay credo.

"I needed an outlet," says Rena, explaining her Mary Kay career. "I was Miss Everything in high school -- the most popular, most athletic, best all-around, a straight-A student. I was planning on college, but then along came Eddie. We fell in love, and so I got married right out of high school.

"I was very happy being Eddie's wife and the mother of my children, but I needed a self-identity. When you get to the point that you're ready to decoupage toilet seats, you know you need an outlet."

The Tarbets also needed the money. "At the time we were living on $300 a month," Rena says. "The highlight of our week was our trip to the grocery store every Friday night."

And so in 1967 Rena went to work for Mary Kay Cosmetics, Inc. Rena is one of more than 200,000 who over the last 17 years have purchased a Mary Kay Beauty Showcase and set themselves up as "consultants" with the company. Currently the forces of Mary Kay comprise about 55,000 women in the United States, Canada, and Australia. Sparkles and Squeals

The lights dim, the show begins. Strobe lights flash and a giant glitter ball throws sparkle throughout the arena to the driving pulse of a rock band. Eight thousand women are on their feet, squealing and clapping. Awards Night is officially under way as a song-and-dance troupe takes the stage singing.

"One singular sensation, every little step she takes. One thrilling combination, every move that she makes; one smile and suddenly nobody else will do . . ."

And in the next 4 1/2 hours several hundred achievers will have a moment in the limelight, receiving lavish recognition in the million-dollar extravaganza for a productive year in sales, sales directorship, or both. From Board Chairman Mary Kay Ash, some will receive keys to pink Cadillacs, the company's most prominent symbol of success. Others will receive diamonds or gold. Others, like Rena Tarbet, will be presented mink coats. And still others will be crowned "queen" for singular achievement.

While most Mary Kay women seem to be content supplementing their husband's ever-decreasing earning power with an average of $500 monthly as consultants and $1,000 as directors, some earn six-figure incomes. Mary Kay says that women will work for recognition when they won't work for money, and that is the thinking behind the company's array of incentive gifts to its top achievers.

These and other prizes are very ceremoniously awarded in a million-dollar pageant heavily copied from the Miss America program. Top women in their respective areas of achievement are crowned "queen" and paraded around a stage to the applause of 8,000 envious onlookers. One recent queen described her crowning this way: "Mary Kay lets us be movie stars for a night. We've all dreamed of it, wanted it. So what if you get it selling cosmetics?" Custom-Tailored

Many of the women who populate the Mary Kay sales force have found it difficult to fulfill themselves -- or, for that matter, simply to earn money -- without fearing that they might upset the very foundation of their lives. Their homes and families are valuable to them, and they don't want to give up their roles as homemakers to go to work. To them Mary Kay offers a custom-tailored solution: a job that can be based in the home but that provides some release from it as well. If she pursues her career with energy and organization, the Mary Kay consultant finds that she can keep her family together and pursue a course toward confidence, achievement, recognition, and considerable wealth. Mary Kay's Empire

Mary Kay Cosmetics was founded 17 years ago in a shopping center storefront by Mary Kay Ash, a retired grandmother who decided she wanted to continue her career in sales, but as her own boss. Today, as chairman of the board, she reins over an empire that couples hard-nose business accumen with femininity and religious probity.

Though its home territory remains its strongest region, the company has expanded rapidly in the northeast over the last seven years. In 1973, Mary Kay opened a manufacturing and distribution facility is Piscataway, N.J., and since that time its number of consultants has more than quadrupled in the 12-state region, which includes the District of Columbia.

One of two cosmetics companies listed on the New York Stock Exchange, Mary Kay has built its business on home-demonstration of its products. Company officials believe that over-the-counter cosmetics sales lack the "educational emphasis" they think women need in order to use skin-care products correctly; they believe the modern American woman is "too sophisticated" for the old door-to-door approach that still characterizes direct sales.

Thus, the "Mary Kay Beauty Show," or party, which the consultant conducts in the home of one of her customers. Each woman there is provided a mirror and makeup palette and applies the various creams and liquefying powders according to the consultant's directions.

"I wanted to give women a chance to go as far as they have the brainpower to go," says Mary Kay Ash from her elaborately furnished executive suite. She herself spent more than 25 years in direct sales, frequently finding herself frustrated in the male-dominated world of business. "I was constantly being told, 'Oh, Mary Kay, you're thinking female.' And inevitably, no matter how well I did my job, I still found myself reaching a golden door marked 'Men Only.'"

So on retirement she took her $5,000 life savings and went into business. The product was to be the cosmetics line she had been buying from a small, private supplier. Well aware of her own limits in working with figures, Mary Kay took as her partner her 20-year-old son, Richard Rogers. She would run the sales force, he would run the business.

From the beginning the company refused to extend credit to consultants. All products, sold at half the retail price, have to be bought with cash only. The reason for this, Rogers explains, is that the most common reason for termination in direct sales is the salesperson's overindebtedness to the company.

Rogers believes Mary Kay has been wise in limiting its line to about 45 products, compared to the 700 or more sold by Avon. (More than half the company's revenue is generated by its basic, five-product skin care set.) With such a manageable inventory, the Mary Kay consultant can keep her business organized with a minimum of time and space.

But the real reason for the growth of the company has been Mary Kay Ash's insight into the psychology of bedrock American womanhood and her ability to use that insight to tap a vast potential labor market: the young-to-middle-aged housewife who is reluctant to leave home to go to work but who wants some kind of career.

First and foremost in the Mary Kay scheme, the company refuses to threaten the family structure. "God first, family second, career third," leads a long list of conforting company bromides. Husbands are offered "Mr. K" classes to instruct them in what their wives are going through, what kind of help they should offer, how to adjust to the changes brought on by a Mary Kay career, and, especially, what benefits to expect. All Over Me!

The most successful women in Mary Kay are those who enter management and become "directors." A director must meet certain quotas for sales and must have recruited a minimum of 22 women working with her to form a "unit."

Then, at her own expense, she travels to Dallas for several days of mandatory orientation. For many of these directors-in-qualification, the trip to Dallas is their first time away from home alone.

One week each month Mary Kay executives welcome a new class of DIQs to the Dallas headquarters. The women in a recent class of 20 (about average) were dazzled by their temporary surroundings. They absorbed the company's dogma as though they were having a religious experience.

They met with top company officials and technicians in white lab coats who conducted them through the stainless steel and tile manufacturing plant. But the highlight was the meeting with Mary Kay herself.

In the morning, the DIQs were in their going-to-church best, awaiting their queen of queens. As Mary Kay entered the door, the DIQs broke into what is called the Mary Kay enthusiasm song, set to a well-known Baptist tune: I've got that Mary Kay enthusiasm Up in my head Down in my heart Down in my feet I've got that Mary Kay enthusiasm All over me, All over me to stay-ay-ay!

Resplendent in a purple Ultrasuede suit and heavy diamonds, blond, wigged Mary Kay Ash seated the group at desks and told of her humble beginnings, how she had cared for an invalid father while her mother worked long days managing a restaurant. She recommended that the DIQs clip grocery coupons to cut bills and Scotch-Guard their Mary Kay uniforms to save on dry cleaning. She also complained about the high cost of Neiman-Marcus blouses.

Toward the end of the morning, Mary Kay began her words of inspiration. She invoked the Golden Rule and then, almost as an act of benediction, gave each DIQ a blue plastic "Golden Rule" marble. "Keep this in your purses at all times," she advised. "Then when you are confused or frightened, clutch the marble in your hand. It will always give you the right answer."

Later that afternoon, Mary Kay had changed into a black caftan and met the DIQs at the door of her circular home she shares with her third husband, Mel. It is customary for Mary Kay to have the DIQs over for spiced tea and cookies on these occasions, and the women look forward to it.

This is the moment most of the DIQs have been waiting for as they walk across the thick, yellow nylon carpet and explore the Ashes' ornate home with Mary Kay's fabled pink bathroom with its sunken tub and Greek statue. Many have cameras and have friends take pictures as they pose in the tub.

Then there is a gathering in the solarium and talk of family values and the rules and benefits of the Mary Kay family and how both family structures can be complementary. Then, with some parting words from Mel, the starry-eyed women are taken to their tour buses and returned to the nearby Marriott Hotel. Vogue and Vague

Having reinforced her family structure, the company proceeds to build the recruit into a confident and poised saleswoman. "Women come to me," Mary Kay is fond of saying, "all Vogue on the outside and vague on the inside. We praise women to success. When one of our girls has had a good day we pat her on the back, pin a little ribbon on her, sing her a song, anything to move her on. If she falls on her face, we pick her up and tell her how gracefully she fell."

Being a Mary Kay consultant or director requires what the company calls "The Mary Kay Image." Dresses are mandatory at Mary Kay gatherings. At last year's convention only two of 8,000 women were in pants, and both apologized personally to Mary Kay -- one explainng that she was new in the company and didn't know about the dress code, the other confiding that she wore leg braces and thought pants more appropriate for her. Alcohol is never served at company functions, because, in Mary Kay's words, "Alcohol and women just don't mix." Good grammar is encouraged, profanity is taboo.

In addition, a Mary Kay woman's life must be pure as cold cream. Richard Rogers recently stated that the company is closed to anyone who is "openly controversial." He added that while a consultant or director can be terminated for bad conduct, she is usually forced out by peer pressure. He cited the example of one woman whose husband was convicted of a felony. The news spread through the company ranks and, according to Rogers, the woman "chose to resign because her husband had brought disgrace on Mary Kay."

Within this way of life, Rena Tarbet has found a measure of fortune and fame she never dreamed would be possible. The Big Moment

It is now 11:30 p.m. on Awards Night. Several hundred Mary Kay winners have been honored. Tennessee Ernie Ford has brought the house down with his gospel show. It is now time for the top 10 directors to be named.

Rena has been called backstage and Eddie has taken his place at the foot of the stage, ready with his Instamatic. Rena entertains a moment of worry. It's possible, she feels, that she and her unit will place as low as fifth. Then the No. 4 director is named and Rena is waiting with two other finalists. The emcee announces, "May I present, ladies and gentlemen, the No. 3 director in all of Mary Kay. From Fort Worth, Texas, a member of the $750,000 club, Rena Tarbet!"

To a standing ovation, Rena receives a kiss and a full-length mink coat, along with other gifts, from Mary Kay Ash. The evening culminates with the crowning of the first-place Shirley Hutton and a grand promenade by Queen Shirley and her court.

Backstage, Rena and Eddie hug and kiss. "I'm aiming for No. 1 next year," Rena exclaims. "I've already got my goals set and my strategy planned."

"And when she wins," says Eddie, "they'll hand me the microphone and I'll get to tell everyone what a wonderful wife and mother Rena is."