ON A SATURDAY MORNING in 1977 in Berkeley, Calif., a 3-year-old girl wandered into her mother's bedroom. Her mother and father were separated; a divorce was imminent. Since the separation, the mother had been sleeping alone, but on this particular morning there was a man in bed with her. The man was the little girl's father. He and his soon-to-be ex-wife had decided to try another go at marriage. The little girl, flushed with joy, ran out of the bedroom yelling: "There's someone in bed with mommy, and it's daddy."

Bill and Carol Eliason of Washington -- married 25 years ago, divorced 12 years ago, remarried 11 years ago -- have worked up a re-marital shtick:

Question: How long have you two been married?

Answer: "Off and on for 25 years."

Bill Eliason, married four times, introduces Carol as "wife number two and four."

They make a point of mentioning the town where they were remarried -- New Hope, Pa.

Seven years ago in southwest Philadelphia, a family therapist named Edna Smalls walked out on her husband, a Baptist preacher. Rev. Leonard Smalls had for 20 years pressured Edna to be a dutiful wife, mother and unpaid servant for his Baptist congregations. Edna divorced her husband in 1975 and moved west to Oakland, Calif., to a new job and new men.

Meantime, Rev. Smalls married a younger woman, divorced her 18 months later and began pining for Edna in Oakland. She'd never fallen out of love with the preacher. When he asked her to come home, she came. After their remarriage one year ago this week, the preacher proudly presented her to the folks at the Church of Christian Compassion. They applauded. Rev. Smalls recalls: "It had a positive effect on their concept of the family."

Remarriage of divorced couples to each other is a strange and unusual occurence in the United States.

"It is like man bites dog," says Ray Fowler, executive director of the American Association for Marriage and Family Therapy. "I'll be darned if I can think of a single one of our 9,000 members who has special knowledge in this area."

It's business as usual for married couples to fight, throw each other out of the house, separate for weeks or months and then get back together. About one-quarter of all married Americans have been separated at one time or another, according to marriage researcher Frank Furstenberg, a University of Pennsylvania sociologist.

Divorce, however, is quite another matter. If separation is the common cold of marriage, divorce is terminal cancer: an agonizing rite of no return for nearly everyone. The mechanics of divorce -- querulous lawyers fanning incompatibility into hatred, skirmishes over property settlements, alimony, child custody and child support -- conspire toward the mutual embitterment of divorced couples. Many marriage counselors say they're astounded when any couple can survive the ravages of divorce with enough intact mutual affection to seriously consider remarriage to each other.

Remarriage to the same spouse happens so rarely, in fact, that, apparently, no social scientist in the United States has ever deemed it significant enough to find out precisely how often it does happen. Experts guess it amounts to less than 1 percent of all remarriages.

Yet, remarriage is booming in America. Fueled by a divorce rate that dooms nearly half of all marriages, the percent of previously married brides and grooms at America's altars has increased dramatically. According to Andrew J. Cherlin, a sociologist at Johns Hopkins University and the author of "Marriage, Divorce, Remarriage," only 3 percent of all brides in 1900 were divorced, as were just 9 percent in 1930. Now nearly 30 percent of the nation's brides are connubial veterans.

Most people who get divorced remarry, and they do it surprisingly fast. Cherlin writes that nearly five out of every six men and about three out of four women remarry, half of them within three years of their divorce.

So, while remarriage to one's ex-spouse represents just a sliver of all remarriages, the great American remarriage boom means that that sliver is probably growing. In 1980, there were a record 2.413 million weddings, according to the National Center for Health Statistics. If one half of one percent of all remarriages involved couples that were once married to each other, then about 7,200 people last year decided to undo the work of their divorce lawyers and move back in with a familiar face.

Men and woman who've remarried each other seem to share a common bit of luck -- neither party was horribly scarred by the divorce. There were few screaming, violent confrontations, no epic wars over house, children or future earnings. Divorce lawyers were kept on a short leash. If any other generalizations can be made about this marital phenomenon that has no definitive statistics, no expert academics, no experienced counselors and a smattering of widely scattered remarried partners, they are:

At least one ex-spouse found that the grass wasn't greener, and

At least one ex-spouse never fell out of love, hanging on in spite of long separation, psychological abuse and a gaggle of "other" woman or men.

Bill Eliason, 56, found that the grass wasn't greener. Carol Eliason, 52, never fell out of love. Their first marriage fell apart in Boston in the mid-1960s. They had three children, one from Bill's first marriage, two together. Carol was a housewife who had followed Bill and his career from Virginia to Texas to Oregon to Boston. Bill had risen in the ranks of the Chrysler Corp. from a dealership manager in Middleburg, Va., to chief executive in charge of the New England region. His success made him feel frisky.

"I wanted out. I was approaching 40 years old. I was reasonably well-paid. I could live pretty high on the hog on my business expense account. I saw housewifery and interest in the kids as more important to Carol than to me. I wanted to have fun. This led to a benign neglect of my marriage and I drifted into another romantic interest," Bill recalls.

Bill became involved with Joan, a writer who had two children of her own. When he was offered a high-paying executive position with Air Products and Chemicals in Allentown, Pa., he and Joan moved there with her children and Bill's son from his first marriage. Carol and her two teen-agers were left behind. The divorce was amicable; Carol was awarded nearly everything but Bill's clothes. She sold their house and moved to a small beach town near Boston.

"I had to learn to live alone. I was very angry. I didn't want the divorce in any way, shape or form. I stalled. I just never really stopped loving him. I was determined I would never say anything to the kids to reduce their love and affecton for him," says Carol.

After Bill left, Carol went to work. She'd never done much with the master's degree in American civilization she earned from the University of Maryland in 1950, but she guessed right about the kind of job that would have a future. She made herself an expert in computer record keeping for colleges. She dated a few men, took care of the kids by herself and surprised herself by surviving.

"I needed to upgrade my sense of self- worth. I didn't know how to fight when we first got married," she says.

Meanwhile, down in Allentown, life was not so rosy for Bill. Joan left him after a year, leaving her kids with him. He was forced to call Carol in Massachusetts and tell her he was running out of money, that he had too many kids to support. Carol, instead of accusing her former husband of niggardly deception, sympathized. Says Bill: "She extended the hand of friendship when I felt desolate. That probably started something stirring again."

In April of 1970, a year after their divorce, Bill and Carol decided to meet for a weekend at Cape Cod. Sparks flew. Within a month, they were remarried in New Hope by a justice of the peace. Carol moved to Allentown and took another college job, but the remarriage was rocky. Bill ran off again to see Joan, came home again and Carol again accepted him back. In 1976, they both decided to get out of Allentown.

"I'd had enough of the corporate wars," says Bill. "We both started a job search. Carol hit before I did. (She was offered a grant to study women in junior colleges. The study resulted in a book, "Neglected Women," and Carol landed a job in Washington as director of the Center for Women's Opportunities at the American Association of Community and Junior Colleges.) We moved to Washington. For the first time in our marriage, I followed Carol."

In Washington, they say their marriage has worked. Bill, director of operations for the non-profit Close-Up Foundation, has learned how to cook and operate the washing machine. Carol, reversing a long practice in their marriage, now gets out of bed first and brings her husband coffee and juice.

"We've learned not to worry about what the moralizers say," says Bill. 'We still bug each other, but now we laugh about it. If one does get angry, the other laughs in his or her face."

Marriage counselors suspect that remarriage to one's ex-spouse, although increasing in absolute numbers because of the remarriage boom, may be declining as a percentage of all remarriage. The reason, according to marriage counselor Ray Fowler in Los Angeles, is that there's an ever-growing pool of divorced and available partners. One's own ex gets lost amid the swarms of everyone else's ex.

Fowler adds: "Increased mobility and increased population significantly diminish the likelihood of staying in the same place long enough to have the former spouse around when you are ready to get remarried."

One anchor that keeps divorced couples in the same geographical area and occasionally forces them to see each other is a kid.

"Even though you can end a marriage, you can never truly break the relationship, particularly if there are children," says Graham Spanier, a professor of human development and sociology at Penn State University and a marriage researcher.

In Berkeley, the little girl who ran downstairs yelling about daddy being in bed with mommy was the catalyst in resurrecting her parents' marriage. The girl's parents, who do not want to be identified because some of their relatives never heard about their divorce, were married in 1970, divorced in 1977 and remarried in 1980. They split up when he was studying film in graduate school at the University of California in Berkeley. She'd dropped out of school and was trying to make a living as a potter. She says they were sexually incompatible. She felt insecure. "We didn't know how life worked," she recalls.

They were brought together one evening when their daughter, on the occasion of her third birthday, demanded that her father come to a party at her mother's house.

"Our daughter insisted that her daddy come to dinner and have spaghetti," says the mother, now 30. "When he came in the house, I remember I said to myself, 'Gosh, he is really attractive.' I hadn't met anyone to compare to him in the year we'd been separated. There was this kind of gut feeling that I had faith in this man. I had a feeling it would be wrong not to try again."

One thing led to another. They met secretly so as not to raise their daughter's hopes. He'd grown up, She no longer felt insecure. In less than a month they allowed their little girl to catch them in bed.

Samuel Johnson sneeringly termed remarriage "the triumph of hope over experience." (He apparently didn't get a chance to address himself specifically to remarrying one's former spouse.) Dr. Johnson's sneer makes some sense in light of studies showing that remarriages don't work out quite as well as first marriages. The Center for Health Statistics estimates that while 67 out of every 100 first marriages begun in 1975 will survive for 10 years, only 52 out of every 100 remarriages will hold up that long. Not s urprisingly, there's no information available on the relative staying power of remarriages between former ex's.

It didn't work for Elizabeth Taylor and Richard Burton. Hollywood is littered with the corpses of revivified marriages. Courts have disallowed tax breaks for couples who marry, divorce and remarry solely in search of larger deductions. Many marriage counselors say they've come across couples who seem to take a perverse pleasure in repeatedly divorcing and remarrying each other. But most counselors and psychiatrists agree that the second tour of marriage is likely to be just as miserable as the first unless both partners grow up during the interum.

"If a couple gets back together just because they lack the courage to be alone, it is more than likely that the remarriage is not going to work," says Craig Messersmith, a marriage counselor at the Washington Psychological Center and a teacher at American University. "But if they get involved in their own growth independent of each other and then perhaps find each other interesting again, it can work."

Edna Smalls, the Philadelphia family therapist who remarried her husband the preacher, agrees: "When I left my husband, I needed to go somewhere and gain self-confidence. Our divorce was amicable. The divorce was about growth and development, nothing else. We divided up our property in an equitable way. I loved my husband. I'd never stop loving him. I told him that when I left."